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Linux and the Flash Storage Revolution
Linux and the Flash Revolution Roland Dreier @rolanddreier June 2014 © 2014 Pure Storage, Inc. | 1 Intro to flash • Who still has a disk Ipod? • Who has switched to a laptop with an SSD? – Did you notice the difference? © 2014 Pure Storage, Inc. | 2 Intro to flash • Who still has a disk Ipod? • Who has switched to a laptop with an SSD? – Did you notice the difference? © 2014 Pure Storage, Inc. | 3 Intro to flash • Who still has a disk Ipod? • Who has switched to a laptop with an SSD? – Did you notice the difference? © 2014 Pure Storage, Inc. | 4 Intro to flash • Who still has a disk Ipod? • Who has switched to a laptop with an SSD? – Did you notice the difference? • Who's running data center apps on disk? © 2014 Pure Storage, Inc. | 5 Flash memory • Hold electrons in a floating gate • Bottom – line: Fast reads without seek time – Writes / erases slower, and wear out flash – Need ECC, wear leveling – [ Retention time, read disturb ] © 2014 Pure Storage, Inc. | 6 Flash memory • Hold electrons in a floating gate • Bottom – line: Fast reads without seek time – Writes / erases slower, and wear out flash – Need ECC, wear leveling – [ Retention time, read disturb ] © 2014 Pure Storage, Inc. | 7 Flash memory • Hold electrons in a floating gate • Bottom – line: Fast reads without seek time – Writes / erases slower, and wear out flash – Need ECC, wear leveling – [ Retention time, read disturb ] © 2014 Pure Storage, Inc. | 8 Flash memory • Hold electrons in a floating gate • Bottom – line: Fast reads without seek time – Writes / erases slower, and wear out flash – Need ECC, wear leveling – [ Retention time, read disturb ] © 2014 Pure Storage, Inc. | 9 Flash memory • Hold electrons in a floating gate • Bottom – line: Fast reads without seek time – Writes / erases slower, and wear out flash – Need ECC, wear leveling – [ Retention time, read disturb ] © 2014 Pure Storage, Inc. | 10 Implications of flash • Disk optimizations like “avoid seeks” or “read sequentially” no longer apply • Need new sophistication (somewhere) to handle flash management and GC • How – do SSDs usually fail in practice? Not flash wear-out... © 2014 Pure Storage, Inc. | 11 Implications of flash • Disk optimizations like “avoid seeks” or “read sequentially” no longer apply • Need new sophistication (somewhere) to handle flash management and GC • How – do SSDs usually fail in practice? Not flash wear-out... © 2014 Pure Storage, Inc. | 12 Implications of flash • Disk optimizations like “avoid seeks” or “read sequentially” no longer apply • Need new sophistication (somewhere) to handle flash management and GC • How – – do SSDs usually fail in practice? Not flash wear-out... Firmware bugs! © 2014 Pure Storage, Inc. | 13 Future non-volatile memory • Many candidates to replace both RAM and flash – MRAM – PCM – ReRAM, memristors, carbon nanotubes, etc. • These technologies are farther away than they appear • Flash is closer than it appears © 2014 Pure Storage, Inc. | 14 Future non-volatile memory • Many candidates to replace both RAM and flash – MRAM – PCM – ReRAM, memristors, carbon nanotubes, etc. • These technologies are farther away than they appear • Flash is closer than it appears © 2014 Pure Storage, Inc. | 15 Future non-volatile memory • Many candidates to replace both RAM and flash – MRAM – PCM – ReRAM, memristors, carbon nanotubes, etc. • These technologies are farther away than they appear • Flash is closer than it appears © 2014 Pure Storage, Inc. | 16 Where to stick your flash • Memory bus • PCIe • SSDs • External boxes (“AFA” / “SSA”) © 2014 Pure Storage, Inc. | 17 Where to stick your flash • Memory bus • PCIe • SSDs • External boxes (“AFA” / “SSA”) © 2014 Pure Storage, Inc. | 18 Where to stick your flash • Memory bus • PCIe • SSDs • External boxes (“AFA” / “SSA”) © 2014 Pure Storage, Inc. | 19 Where to stick your flash • Memory bus • PCIe • SSDs • External boxes (“AFA” / “SSA”) © 2014 Pure Storage, Inc. | 20 Where to stick your flash • Memory bus • PCIe • SSDs • External – boxes (“AFA” / “SSA”) Appliance or array? – FC, iSCSI, IB,… ? © 2014 Pure Storage, Inc. | 21 Linux tech © 2014 Pure Storage, Inc. | 22 Free space management • Help GC • Discard • fstrim AKA TRIM AKA UNMAP vs. -o discard © 2014 Pure Storage, Inc. | 23 Free space management • Help GC • Discard • fstrim AKA TRIM AKA UNMAP vs. -o discard © 2014 Pure Storage, Inc. | 24 Free space management • Help GC • Discard • fstrim AKA TRIM AKA UNMAP vs. -o discard © 2014 Pure Storage, Inc. | 25 Caching • dm-cache and bcache • Performance is highly dependent on workload © 2014 Pure Storage, Inc. | 26 Caching • dm-cache and bcache • Performance is highly dependent on workload – One disk IO can ruin your whole second © 2014 Pure Storage, Inc. | 27 NVMe • New storage protocol optimized for high perf, parallel devices • nvme driver in Linux since kernel 3.6 © 2014 Pure Storage, Inc. | 28 block mq • Storage • Don't devices and CPUs are getting more parallel want a single lock per storage device • Making its way upstream now © 2014 Pure Storage, Inc. | 29 Are you using flash? Your competitors are. © 2014 Pure Storage, Inc. | 30 Thank You! © 2014 Pure Storage, Inc. | 31
