RamDisk and RamDisk Plus

Transcription

RamDisk and RamDisk Plus
What are RamDisk and RamDisk Plus?
RamDisk and RamDisk Plus allow you to add, modify and remove RAM disks from your system.
RamDisk Plus allows you to add multiple RAM disks, supports variety of different kinds of RAM
disks, and can load a RAM disk image file, presenting its contents as a read-only disk. In
addition, RamDisk Plus provides the ability to access main memory that many Windows®
32-bit editions do not support.
SuperSpeed's RamDisk products are also used in embedded environments, and our RAM disks
have been deployed as bootable RAM disks.
Copyright © 2012 SuperSpeed LLC. All rights reserved.
SuperSpeed®, SuperCache®, SuperCache II®, SuperVolume®, and RamDisk Plus® are
registered trademarks of SuperSpeed LLC.
Microsoft, Windows, Windows 2000, Windows XP, Windows Vista, Windows 7, Windows Server
2003, Windows Server 2003 R2, Windows Server 2008, and Windows Server 2008 R2 are
trademarks of Microsoft Corporation.
This software may be protected by one or more of the following patents: US patent numbers
5,577,226, 5,606,681, 5,918,244, 6,370,615, 6,629,201, 6,651,136, 7,017,013, 7,039,767,
7,111,129, 7,475,186, 7,594,068, 7,631,139, and other patents pending.
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RamDisk Plus
RamDisk Plus features a host of options to maximize performance and utility. RamDisk Plus
supports up to 99 RAM disks. Each RAM disk can be built on specific NUMA nodes. On PAE
machines, RAM disks can be created from memory not managed by Windows (ie. Unmanaged
Memory), recapturing that lost system resource.
RamDisk Plus also features full management of a RAM disk's image file. A RAM disk's contents
can be preserved across system restarts making it behave very much like a hard drive. It's
contents can also be backed up and restored to user-specified files. In addition, image files
can be loaded as read-only disks and their contents browsed and extracted.
Depending on the system, RAM disks as large as 63 GB (32-bit) or 16 TB (64-bit) can be
created. The RAM disk can identify itself to Windows as a hard disk, as a removable-media
disk, or as a virtual disk. It can be formatted with any Windows-supported file system.
Security features are also available with RamDisk Plus. The 'zero' option ensures that the
entire contents of a RAM disk is zeroed (wiped clean) when it is removed from the system or
when a new image is restored to it. The Auto-Wipe feature zeroes (wipes clean) the contents
of each RAM disk present in the system and reloads its initial (boot) image each time a user
logs out. This is useful in a secure environment where multiple users have access to a
workstation and its resources, but only one at a time, and the contents of RAM disk resources
must be completely destroyed at the end of a user session.
RAM disks are available to the system very early in system startup. Therefore, any
applications or services that depend on the RAM disk can access it as soon as they start.
RAM disks created with RamDisk Plus also support page files.
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RamDisk
RamDisk allows you to create a single RAM disk using available physical memory from Windows.
Depending on the system, a RAM disk as large as 63 GB (32-bit) or 16 TB (64-bit) can be
created. The RAM disk can appear to Windows as a hard disk, as a removable-media disk, or
as a virtual disk. It can be formatted with any Windows-supported file system.
An important feature of RamDisk is that the RAM disk it creates is available to the system very
early in system startup. Therefore, any applications or services that depend on the RAM disk
can access it as soon as they start.
RamDisk provides basic, simple support for a single RAM disk. For multi-disk, data persistence,
NUMA, Unmanaged Memory support, auto-wipe (security), and other features, see RamDisk
Plus.
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File menu commands
The File menu offers the following commands:
Auto-Wipe (dialog)
Display status of and configure the auto-wipe-at-logoff service.
Licensing (dialog)
Display and update licensing information.
Memory (dialog)
Display and configure memory information.
Options (dialog)
Display and set application options.
Exit
Exits the application.
Action menu commands
The Action menu offers the following commands*:
Add (property sheet)
Adds a new RAM disk to the system.
Add (simple wizard)
Adds a new RAM disk to the system with basic options.
Add (advanced wizard)
Adds a new RAM disk to the system with all options.
Load (property sheet)
Loads a new RAM disk to the system from an image file.
Load (simple wizard)
Loads a new RAM disk to the system from an image file with basic
Load (advanced wizard)
Loads a new RAM disk to the system from an image file with all opt
View (property sheet)
Views the contents of a RAM disk image file.
View (wizard)
Views the contents of a RAM disk image file.
Save (dialog)
Saves the contents of a RAM disk to its associated image file.
Backup (dialog)
Backs up the contents of a RAM disk to an image file.
Restore (dialog)
Restores the contents of a RAM disk from an image file.
Remove (dialog)
Removes a RAM disk or an Image View from the system.
Properties (property sheet)
Display and modify the properties of a RAM disk or an Image View.
Help menu commands
The Help menu offers the following commands, which provide you assistance with this
application:
Help Topics (new window)
Offers you an index to topics on which you can get help.
About (dialog)
Displays the version number of the application.
*The type of graphical user element (ie. property sheet, simple or advanced wizard) that the
Add, Load and View commands use is determined by the Options settings.
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Save dialog
Do not enforce volume locking
This option allows the RAM disk to be written to its associated image file without locking the
storage volume(s) present on the RAM disk. This means that handles may still be opened to
the disk when it is saved.
WARNING: Using this option can result in an image file that contains corrupt files and/or file
systems.
Because of the risks involved, this option generally is used only when it is impossible to close
all handles to the RAM disk.
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Backup RAM Disk dialog
Image file
Describes the path of the file to which the RAM disk's image will be saved.
Volume locking
This option allows the RAM disk to be written to its associated image file without locking the
storage volume(s) present on the RAM disk. This means that handles may still be opened to
the disk when it is saved.
WARNING: Using this option can result in an image file that contains corrupt files and/or file
systems.
Because of the risks involved, this option generally is used only when it is impossible to close
all handles to the RAM disk.
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Restore dialog
Image file
Describes the path of the file from which the RAM disk's image will be restored.
Zero memory before restoring
Select this option to completely erase (destroy) the contents of the RAM disk before restoring
its contents with the selected image file.
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Remove dialog
Keep image file
Select this option to preserve the RAM disk's associated image file. The RAM disk can later be
re-instantiated with the image file's contents using the 'Load RAM disk' command.
Zero memory
Select this option to completely erase (destroy) the contents of the RAM disk.
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Auto-Wipe dialog
Information
This dialog configures and displays the current status of the auto-wipe feature. This feature is
available only for RamDisk Plus.
Install/Uninstall
Click to Install/Uninstall the auto-wipe-at-logoff service.
Important:
This feature is intended for use in secure environments where one and only one user is logged
on to the machine at any time. When this feature is enabled, the auto-wipe service will
monitor all user logon and logoff events. At logoff, the service will dismount each RAM disk
present in the system, zero (wipe) its contents, and then restore its original image using its
associated image file.
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About dialog
This dialog displays information about the product and application, including their version and
copyright.
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Licensing dialog
Information
This dialog displays information about the product's license, including the status, licensee,
product(s) and platform(s) licensed, copyright, etc.
Update Key
Click this button to update the software license.
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Update Key dialog
Information
This dialog displays information about the product's license, including the status, licensee,
product(s) and platform(s) licensed, copyright, etc.
License file
The location of the license key file.
Apply
Click to update (replace) the active key with the new key specified by the license file.
Browse...
Click to browse for the new license key file.
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Memory Information dialog
Page size
The size of a physical page of memory, in bytes.
NUMA node count
The number of NUMA (Non-Uniform Memory Architecture) nodes reported by the system.
NUMA node mask
The hexadecimal mask of the NUMA nodes reported by the system.
Memory available
Displays information about amounts of memory installed, available and reported by Windows. If
Unmanaged Memory (UM, memory not managed by Windows) is configured, information about
it is also included.
PFN Info
Click this button for information about available PFN ranges.
Unmanaged
Click this button to view and configure Unmanaged Memory.
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PFN Information dialog
This dialog displays PFN information only if Unmanaged Memory has been configured for Direct
Address. Direct Address supports the creation of RAM disks in areas of contiguous physical
memory, at specific physical memory addresses.
Page size
The size of a physical page of memory, in bytes.
First unmanaged PFN
The first PFN (Page Frame Number) after the last PFN reported as managed by the system.
Last detected PFN
The last PFN detected as valid memory.
Available PFN ranges
A list of ranges of unallocated PFNs.
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Unmanaged Memory Information dialog
Active values are those currently in use by the Virtual bus device. Pending values are those
that will be in use when the Virtual bus device is restarted.
Installed (MB)
The amount of system RAM (main memory) installed, in megabytes.
Reserved (MB)
The amount of system RAM (main memory) reserved for use by a video adapter, the system
BIOS, etc.
Direct Address
Disabled for dynamic allocation of unmanaged memory. Enabled for direct address of
unmanaged memory.
Configure
Click this button to configure Unmanaged Memory.
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Configure Unmanaged Memory dialog
Enable use of Unmanaged Memory
Select to enable the use of Unmanaged Memory (UM).
Use System Management BIOS value
Select to use the amount of system RAM (main memory) reported by the System Management
BIOS as the Installed value. At times the value reported using the System Management BIOS
API may not be accurate. This option permits the Installed amount to be entered manually.
Automatically search for Reserved value
Select to search the physical memory address space for the Reserved value of system RAM
(main memory). At times the value determined by the software may not be accurate. This
option permits the Reserved amount to be entered manually.
Installed (MB)
The amount of system RAM (main memory) installed, in megabytes.
Reserved (MB)
The amount of system RAM (main memory) reserved for use by a video adapter, the system
BIOS, etc. If the system shares main memory with a video adapter, the amount of reserved
memory may depend on the resolution and color depth of the display.
Direct Address
Disable for dynamic allocation of unmanaged memory. Dynamic allocation allows unmanaged
memory to be allocated dynamically along with the memory managed by Windows.
Enable for direct address of unmanaged memory. Direct address allows a RAM disk to be
allocated from unmanaged memory as a single block of contiguous pages.
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Options dialog
User interface method
The operations to add or load a RAM disk or to view a RAM disk image file have many options
which can be confusing. The wizards present the various options in a logical sequence. For
step-by-step access to the options, select Use wizards. To see only the most frequently
used options, unselect Use advanced wizards. To see all the available options, select Use
advanced wizards. For quick access to all options, select Use property sheets.
Main window
Remember window placement
Saves the desktop location of the application's window when it is closed.
Remember window size
Saves the size of the application's window when it is closed.
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NUMA Nodes dialog
Memory allocation nodes
Selects the NUMA nodes from which memory will be allocated. NOTE: If unmanaged memory is
configured, memory for the RAM disk will be allocated from unmanaged memory first. NUMA
affinity information is not available for unmanaged memory, so the nodes here selected will be
ignored.
Select all
Check this box to allocate RAM disk memory from all NUMA nodes.
Clear all
Click this button to unselect all NUMA nodes. At least one node must be selected to create a
RAM disk.
0, 1, 2, 3, ...
The individual NUMA nodes from which the RAM disk allocation will be made. On NUMA
machines, a RAM disk's allocation is composed of a series of 1 MB allocations, each taken from
a NUMA node in the selection, in round-robin fashion
.
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Progress dialog
This dialog displays progress activity for a particular operation.
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Add - Advanced Wizard
This wizard presents all the available options for creating a new RAM disk. Its advantage over
the Add property sheet is the logical order in which the options are presented. This helps
reduce confusion due to the interdependency of many of the options.
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Size advanced wizard page
Size of the RAM disk, in megabytes
Specify the size of the RAM disk to be created. The maximum size is limited by the amount of
physical memory (RAM) installed in the system.
Zero memory when removed or restored
Select to zero (erase) the contents of the entire RAM disk when it is removed or when an
image is restored to it.
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Allocation Source advanced wizard page
Allocate from Windows-managed memory
Select to allocate the RAM disk's memory from memory managed by Windows. NOTE: If
Unmanaged Memory (UM) is configured, allocations will first be attempted from UM and then
from Windows.
Direct address memory NOT managed by Windows
Select to allocate the RAM disk's memory from memory not managed by Windows, or
Unmanaged Memory (UM). This option is only available if UM is configured with Direct Address
enabled.
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NUMA Nodes advanced wizard page
Selects the NUMA nodes from which memory will be allocated. NOTE: If Unmanaged Memory
(UM) is configured, memory for the RAM disk will be allocated from UM first. NUMA affinity
information is not available for UM, so the selected nodes will be ignored for UM allocations.
Select all
Clear all
RAM disk.
0, 1, 2, 3, ...
a NUMA node in the selection, in round-robin fashion.
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Base PFN advanced wizard page
Automatically assign PFN
Select to allow the application to choose the PFN.
Manually assign PFN base / Base PFN
Select to enter the base PFN of the physical memory range which the RAM disk will occupy, in
hexadecimal.
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Device Type advanced wizard page
Partitionable - detected by Windows as a hard disk
Select to create a RAM disk that Windows will detect as a hard disk. This disk will support a
partition table, and can be managed by the Disk Management MMC.
Removable - detected by Windows as a removable media device
Select to create a RAM disk that Windows will detect as a hard disk with removable media.
Virtual - detected by Windows as a RAM disk
Select to create a RAM disk that Windows will detect as RAM disk, not a hard disk. This disk
will not support a partition table.
Version 8.0 - compatible with previous versions of RamDisk
Select to create a RAM disk that is compatible with RamDisk 8.0 and RamDisk Plus 8.0.
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Partitioning advanced wizard page
Create a partition table
Select to create a partition table. NOTE: This option is not available for version 8 RAM disks,
nor for virtual RAM disks.
Use a GUID partition table
Select to create a GUID-type partition table. NOTE: This option is valid on 64-bit platforms
only.
Create a partition table entry
Select to insert an entry in the partition table. The partition entry will span the entire RAM
disk.
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Drive Letter and File System advanced wizard page
Specify the drive letter to assign the RAM disk
Select a drive letter to assign to the partition of a RAM disk containing a partition table and
entry, or, in the case of a version 8 RAM disk or a virtual disk (which have no partition table),
to the disk itself.
Specify the file system to format the RAM disk
Select a file system format for the partition of a RAM disk containing a partition table and
entry, or, in the case of a version 8 RAM disk (which has no partition table), for the disk itself.
Note: if selected, a virtual disk is formatted by the class driver at the time of its creation with
a FAT-type file system only.
Create '\temp' folder
Select to create a folder named "temp" in the root of the RAM disk.
Compress file system
Select to compress the contents of the entire file system. For NTFS only.
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Associated Image File advanced wizard page
Use associated image file
Select to create and maintain an image file that is associated with the RAM disk. For RAM
disks containing a partition table and for version 8 RAM disks the associated image file is used
to save or restore disk's contents between system reboots. This feature is especially
important since for such RAM disks any file system metadata (eg. the "format" information) is
lost when the system is shutdown or restarted. When a RAM disk with an associated image file
is re-instantiated, its image is read from the image file, thus restoring the file system and any
other saved data. Without the associated image file, such a RAM disk will have no file system
at all when the system is started. NOTE: generally, virtual RAM disks are formatted at the
time they are instantiated and so do not require an associated image file.
Location of associated image file
Specifies the drive letter of the root directory in which the RAM disk's associated image file
will be placed. A RAM disk's associated image file is always located in the root directory of a
drive. By default, it is located in the root of the boot drive (the partition containing the active
Windows installation). The file is marked hidden. Its name is "SsRdXxxx.cif", where Xxxx
represents the four-digit identifier assigned to the RAM disk.
Save at system shutdown
Select to save the contents of the RAM disk to its associated image file at system shutdown.
This option effectively makes the RAM disk persistent across reboots.
Reserve space for full disk
Select to expand the size of the associated image file to the largest necessary to contain the
entire RAM disk's contents. This option does not specify that the entire RAM disk be saved. It
specified that sufficient space be reserved on the partition containing the associated image
file, so that if the entire RAM disk had to be saved it could be.
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Add - Simple Wizard
This wizard presents the most frequently used options for creating a new RAM disk.
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Size wizard page
Specify the size of the RAM disk, in megabytes
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Drive Letter wizard page
Select a drive letter to assign the RAM disk. Drive letters already used by local drives are not
shown. Take care not to select a drive letter that is used by a network drive.
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File System wizard page
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Save at Shutdown wizard page
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Zero Contents wizard page
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Load - Advanced Wizard
This wizard presents all the available options for creating a RAM disk from an existing image
file. Its advantage over the property sheet is the logical order in which the options are
presented. This helps reduce confusion due to the interdependency of many of the options.
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Image File advanced wizard page
Select the root directory containing the associated image file
Specify the drive letter of the root directory in which the RAM disk's associated image file is
located. A RAM disk's associated image file is always located in the root directory of a drive.
By default, the file is placed in the root of the boot drive (the partition containing the active
Windows installation).
Select the associated image file's identifier
Specify the four-digit identifier of the RAM disk's image file. When a RAM disk is initially
created, it is assigned a four-digit identifier. This identifier uniquely identifies the disk. If the
disk is created with an associated image file, the file's name and contents are linked to the
RAM disk using the identifier. As long as the RAM disk remains in the system, its identifier will
not change.
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Allocation Source advanced wizard page
from Windows.
enabled.
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NUMA Nodes advanced wizard page
Selects the NUMA nodes from which memory will be allocated. NOTE: If Unmanaged Memory
(UM) is configured, memory for the RAM disk will be allocated from UM first. NUMA affinity
information is not available for UM, so the selected nodes will be ignored for UM allocations.
Select all
Clear all
RAM disk.
0, 1, 2, 3, ...
a NUMA node in the selection, in round-robin fashion.
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Base PFN advanced wizard page
Manually assign PFN base / Base PFN
Select to enter the base PFN of the physical memory range which the RAM disk will occupy, in
hexadecimal.
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Drive Letter advanced wizard page
to the disk itself.
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Save at Shutdown advanced wizard page
Automatically save the RAM disk's contents at system shutdown
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Load - Simple Wizard
This wizard presents the most frequently used options for creating a RAM disk from an existing
image file.
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Image File wizard page
Select the root directory containing the associated image file
Select the associated image file's identifier
Specify the four-digit identifier of the RAM disk's image file. When a RAM disk is initially
created, it is assigned a four-digit identifier. This identifier uniquely identifies the disk. If the
disk is created with an associated image file, the file's name and contents are linked to the
RAM disk using the identifier. As long as the RAM disk remains in the system, its identifier will
not change.
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Select a drive letter to assign the RAM disk. Drive letters already used by local drives are not
shown. Take care not to select a drive letter that is used by a network drive.
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Save at Shutdown wizard page
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View - Wizard
This wizard presents all the available options for creating a view of a RAM disk image that is
stored in an image file. The view is effectively a read-only RAM disk. Only a minimal amount of
memory is allocated to create the view.
Use image views to retrieve data from RAM disk image files stored on disk, without having to
create a RAM disk. A view allows you to access a saved RAM image that may be much larger
than the amount of available memory.
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Image File wizard page
Image file location
Specify the path of the image file to be viewed.
Browse...
Click to open an "Open File" dialog box to browse for an image file.
Examine
Click to examine the contents of the specified file.
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Specify the drive letter to assign the read-only RAM disk
Select a drive letter to assign the read-only RAM disk. Drive letters already used by local
drives are not shown. Take care not to select a drive letter that is used by a network drive.
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Add - Property Sheet
This property sheet presents all the available options for creating a new RAM disk. Its
advantage over the Add wizards is its immediate access to all the options.
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Size property page
Size of the RAM disk, in megabytes
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Memory property page
from Windows.
NUMA Nodes
Click to select from which NUMA nodes to allocate the RAM disk's memory. NOTE: This does
not apply to UM allocations.
enabled.
Base PFN
Enter the base PFN of the physical memory range which the RAM disk will occupy, in
hexadecimal.
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Type property page
Partitionable - Windows hard disk
Select to create a RAM disk that Windows will detect as a hard disk. This disk will support a
partition table, and can be managed by the Disk Management MMC.
Removable - Windows removable media device
Select to create a RAM disk that Windows will detect as a hard disk with removable media.
Virtual - Windows RAM disk
Select to create a RAM disk that Windows will detect as RAM disk, not a hard disk. This disk
will not support a partition table.
Version 8.0 - compatible with RamDisk 8.0
Select to create a RAM disk that is compatible with RamDisk 8.0 and RamDisk Plus 8.0.
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Partitioning property page
Create a partition table
Select to create a partition table. NOTE: This option is not available for version 8 RAM disks,
nor for virtual RAM disks.
Use a GUID partition table
Select to create a GUID-type partition table. NOTE: This option is valid on 64-bit platforms
only.
Create a partition table entry
Select to insert an entry in the partition table. The partition entry will span the entire RAM
disk.
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Drive Letter and File System property page
to the disk itself.
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Image File property page
will be placed. A RAM disk's associated image file is always located in the root directory of a
Windows installation). The file is marked hidden. Its name is "SsRdXxxx.cif", where Xxxx
represents the four-digit identifier assigned to the RAM disk.
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Load - Property Sheet
This property sheet presents all the available options for creating a RAM disk from an existing
image file. Its advantage over the Add wizards is its immediate access to all the options.
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Root directory of the Associated Image File
Associated Image File identifier
Specify the four-digit identifier of the RAM disk. When a RAM disk is initially created, it is
assigned a four-digit identifier. This identifier uniquely identifies the disk. If the disk is created
with an Associated Image File, the file's name and contents are linked to the RAM disk using
the identifier. As long as the RAM disk remains in the system, its identifier will not change.
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Memory property page
from Windows.
NUMA Nodes
Click to select from which NUMA nodes to allocate the RAM disk's memory. NOTE: This does
not apply to UM allocations.
enabled.
Base PFN
Enter the base PFN of the physical memory range which the RAM disk will occupy, in
hexadecimal.
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Drive Letter property page
Drive letter to assign the RAM disk
to the disk itself.
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Save at Shutdown property page
Automatically save the RAM disk's contents at system shutdown
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View - Property Sheet
This property sheet presents all the available options for creating a view of a RAM disk image
that is stored in an image file. The view is effectively a read-only RAM disk. Only a minimal
amount of memory is allocated to create the view.
Use image views to retrieve data from RAM disk image files stored on disk, without having to
create a RAM disk. A view allows you to access a saved RAM image that may be much larger
than the amount of available memory.
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Image file location
Specify the path of the image file to be viewed.
Browse...
Click to open an "Open File" dialog box to browse for an image file.
Examine
Click to examine the contents of the specified file.
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Drive Letter property page
Drive letter to assign the read-only RAM disk
Select a drive letter to assign to the partition of a RAM disk image containing a partition table
and entry, or, in the case of a version 8 RAM disk or a virtual disk image (which have no
partition table), to the disk itself.
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Properties
This property sheet display the current RAM disk or Image View settings. It can also be used
to modify the settings.
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Properties page
Description
Details the properties of the RAM disk.
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Settings page
This page contains the changeable settings of the RAM disk.
Drive letter assigned to the RAM disk
to the disk itself.
will be located. A RAM disk's associated image file is always located in the root directory of a
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The 32-bit Address Space
The following information pertains to processors capable of running 32-bit Microsoft Windows
operating systems.
What is a 32-bit address space?
An address space is a logical area or space containing one or more locations that can be
individually accessed or addressed. A 32-bit address space describes an area containing a
maximum possible 4,294,967,296 locations or addresses. A 32-bit operating system, therefore,
would typically be limited to access 4,294,967,296 pieces of computer information, or bytes (4
GB).
Address spaces on 32-bit Windows-compatible hardware
Computers that run Windows operating systems actually utilize two different kinds address
spaces: a memory address space and an I/O port address space. The memory address space
is where main memory (RAM) is accessed, while devices (network, video, disk, etc.) typically
use both memory and I/O address spaces.
Furthermore, memory is accessed through two different kinds of address spaces: physical and
virtual. The virtual address space is what applications and processes "see" and use. One of
the most important purposes of virtual address space is that it can present to applications
and processes more memory than is physically present in the machine. A virtual address may
or may not correspond to a real, physical address. The physical address space is where real,
physical memory, or memory-addressed devices, are accessed.
As noted above, a 32-bit processor's memory address space is used to access both main
memory (RAM) and devices that require memory addresses. Since the devices (called
"memory-mapped" devices) may consume a considerable amount of memory address space,
much less than the full 4 GB address space may be available for accessing main memory. See
Memory Managed by Windows to see how Windows handles this problem.
However, with special hardware and software, 32-bit processors can address much more than
4 GB. See Physical Address Extensions for how this is possible.
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Physical Address Extensions (PAE)
What are Physical Address Extensions?
Physical Address Extensions, or PAE, are a set of hardware specifications that extend a 32-bit
processor's physical memory address space to a maximum of 36 bits, thus providing support
for up to 64 gigabytes of memory. Depending on the hardware, the memory address space
may be 33, 34, 35 or 36 bits wide. These represent 8, 16, 32, and 64 gigabyte address
spaces.
It's worth repeating that PAE defines hardware that supports physical address spaces larger
than 32 bits. However, taking advantage of these larger address spaces requires more than a
PAE-compatible processor and chipset (on the mainboard): it requires a PAE-enabled operating
system. Operating systems that are "unaware" of PAE will run on PAE hardware but "see" only
a 32-bit (4 GB) address space.
Happily, all 32-bit Windows operating systems from Windows 2000 forward support PAE mode.
See Memory Managed by Windows for more about how Windows supports PAE. See
Unmanaged Memory for information about how RamDisk Plus supports PAE.
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Memory Managed by Windows
Non-PAE Systems
Windows operating systems come in two basic editions: 32-bit and 64-bit. Logically, 32-bit
editions of Windows run on 32-bit processors, many of which, along with their chipset,
implement 32-bit memory and I/O address buses. These non-PAE machines can address a
maximum of 4,294,967,296 bytes (4 gigabytes, GB), per address space. (For more about PAE,
see Physical Address Extensions.)
On Windows computers, the base 4 GB memory address space is not devoted exclusively to
main memory. Video, network, disk, and other devices also require memory address space.
Because of this, only a reduced amount of the 4 GB address space is actually available to
main memory.
In order to eliminate a host of problems associated with the device drivers that require
memory address space, starting with Windows XP SP2 Microsoft has limited the amount of
main memory accessible in the 4 GB address space to approximately 3.2 GB. Therefore, even if
a non-PAE machine has more than 3.2 GB of main memory installed, only 3.2 GB of it will be
accessible to Windows. The remaining 0.8 GB of address space is reserved for
memory-mapped devices.
For machines that do not have PAE hardware, this access limit to main memory cannot be
overcome. It is a hardware limitation.
PAE Systems
On machines with PAE hardware, all main memory can be access -- at least theoretically. For
Windows to access the memory, it must also be running in PAE mode. All 32-bit Windows
operating systems from Windows NT 4.0 forward support PAE, including 32-bit Windows XP,
Vista and 7. To determine if Windows is running in PAE mode, open the System Properties
dialog and select the General tab. If PAE is enabled the text "Physical Address Extensions" will
appear near the bottom of the dialog.
Depending on the edition and applied service pack, Windows operating systems provide
different facilities for enabling PAE. (See “Boot Parameters to Configure DEP and PAE”
http://msdn.microsoft.com/en-us/library/aa468629.aspx, “/noexecute”
http://msdn.microsoft.com/en-us/library/ms791539.aspx, “/execute”
http://msdn.microsoft.com/en-us/library/aa468631.aspx, “/nopae”
http://msdn.microsoft.com/en-us/library/ms791508.aspx, “/pae”
http://msdn.microsoft.com/en-us/library/ms791485.aspx.)
On PAE-enabled machines, Windows versions from XP SP2 forward still dedicate the upper 0.8
GB of the first 4 GB of memory address space to memory-mapped devices. However, if
Windows is running with PAE mode enabled, then it is capable of accessing whatever amount
main memory is installed after the first 3.2 GB, up to a total of 64 GB. This memory simply will
be mapped to start above the first 4 GB of address space. In other words, assuming the
machine has more than 3.2 GB of main memory, the first 3.2 GB of memory will be accessible in
the lower 3.2 GB of memory address space, while the remaining main memory will be accessible
at addresses starting at and above 4.0 GB.
Even so, Microsoft has imposed limits on what each edition of 32-bit Windows will access, or
manage, even if PAE mode is enabled. Here are the limits:
32-bit Windows Edition
Windows XP SP2, Windows Vista, Windows
7
Maximum managed memory (GB)
w/o PAE
w/PAE
3.2
3.2
Page 75
Windows Server 2003, 2003 R2, 2008,
2008 R2, Standard edition or lesser
3.2
4.0
Notice that Windows XP SP2, Windows Vista and Windows 7 have the same memory limits
whether running in PAE mode or not.
Overcoming the Windows Memory Barrier
The fact is, with "extra help" all 32-bit PAE-enabled editions of Windows can support up to 64
GB of main memory -- the PAE hardware limit. SuperSpeed's RamDisk Plus product provides
that "extra help" by supporting what we call "Unmanaged Memory". See Unmanaged Memory
for information about how RamDisk Plus supports memory not managed by Windows.
Page 76
Unmanaged Memory
With PAE-mode enabled, all 32-bit Windows editions can potentially access up to 64 GB of
main memory. Nonetheless, different Windows editions limit the amount of main memory they
support to 4 GB or less.
SuperSpeed's RamDisk Plus features support to utilize main memory that Windows does not.
What is unmanaged memory?
We call the main memory that Windows does not use or manage "Unmanaged Memory", or UM.
On a machine running 32-bit Windows XP SP2, Windows Vista, or Windows 7 with 4 GB of main
memory installed and with PAE mode enabled, Windows typically limits the amount of main
memory available to about 3.2 GB. This leaves about 0.8 GB of main memory unused or
unmanaged by Windows.
With RamDisk Plus, that 0.8 GB of main memory unused or unmanaged by Windows
(Unmanaged Memory, UM) can now be put to work! What's more, UM can be used right along
with the physical memory that Windows manages. In the case described above, RamDisk Plus
can create a RAM disk as large as 3.5 GB! On a machine running 32-bit Windows XP SP2 or
Vista with 8 GB of main memory installed and with PAE mode enabled, a RAM disk up to 7.5 GB
can be created!
Put as Much RAM as You Have and Need to Work
RamDisk Plus thus reclaims the memory resources that would otherwise be lost or unusable.
This provides greater versatility in the use of Windows operating systems and applications
that can benefit from the increased performance afforded by RAM disks. Now any 32-bit
PAE-enabled edition of Windows can access up to 64 GB of main memory, using the bulk of it
to enhance system performance!
RamDisk Plus supports two methods to access UM: dynamic and static. Dynamic access, or
dynamic allocation, allows UM to be used transparently along with the physical memory
managed by Windows. Static access, or direct address, allows specific blocks of physical
memory to be allocated for RAM disks.
Page 77
Dynamic Allocation of Unmanaged Memory
What is dynamic allocation?
Dynamic allocation allows Unmanaged Memory (UM) to be allocated in a fashion similar to how
Windows allocates physical memory pages. When a RAM disk is created, memory is first
allocated from any unallocated UM, and then from unallocated Windows-managed memory.
When a RAM disk is removed, the physical memory allocated to it is returned -- either to the
pool of physical pages that Windows manages, or to the UM pool that RamDisk Plus manages.
For example, on a 32-bit, PAE-enabled Windows XP, Windows Vista or Windows 7 system with
8 GB of main memory, typically about 3.2 GB is managed by the operating system. Ordinarily, a
RAM disk of only some 2.5 GB could be created. With RamDisk Plus and the UM feature
properly configured, the additional 4.8 GB of UM also would be available. Therefore, a single
RAM disk of 7 GB or more (4.8 GB UM, 2+ GB Windows-managed) could be created.
Generally, dynamic allocation is as it offers the simplest and most flexible method to use UM.
Page 78
Direct Address of Unmanaged Memory
What is direct address?
Direct address allows Unmanaged Memory (UM) to be allocated as a single block of contiguous
physical memory pages. A base or starting physical address must be specified in the form of a
Page Frame Number (PFN). The number of physical memory pages used for the RAM disk is
determined by the RAM disk's size.
Generally, RAM disks created with direct address of UM are used in embedded environments.
Direct address does NOT support RAM disks created from memory managed by Windows.
Page 79

RamDisk and RamDisk Plus

Transcription

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