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Hybrid Storage Technologies: An Overview

This presentation provides an overview of hybrid storage technologies, including solid-state drives (SSDs), their benefits, Sun's SSD strategy and portfolio, and the use of ZFS and the hybrid storage pool. It also discusses the need for improved storage balance in modern systems and the advantages of SSDs over traditional hard disk drives (HDDs).

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Hybrid Storage Technologies: An Overview

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  1. An overview on Hybrid Storage Technologies Paolo Bianco Storage Architect Sun Microsystems

  2. An overview on Hybrid Storage Technologies • Agenda • The Storage Evolution • Anatomy of an SSD • Why Solid State Drives? • Sun SSD Strategy and Portfolio • ZFS and the Hybrid Storage Pool ... instead of buying several dozens of high speed low capacity drives

  3. Disk to CPU DiscontinuityToday’s CPU have become I/O starved • CPU Performance Improvement in 6Y = 10x • HDD Performance improvement in 6Y = 1,5x • As a result, storage systems are hopelessly unbalanced between controller capability and storage pool performance

  4. Why IOPS matter(usually more than transfer rate) For many accesses, the non-transfer time component is dominant. IOPS is one metric reflecting this component.

  5. Storage EvolutionTime for a change?

  6. New Server Memory Hierarchy

  7. SSDs Keep Up w/ CPUMoore’s Law controls both

  8. Anatomy of an SSD

  9. NAND Basics • Single Level Cell (SLC) • 30MB/sec per Die (Write) • Data Retention: 10 years • Endurance: 100,000 cycles • 1.8-2.0x price of MLC • 45 nm SLC has ~ 500 electrons in the floating gate • Focus on reliability and performance • Multi Level Cell (MLC) • 10MB/sec per Die (Write) • Data Retention: 3-4 years • Endurance: 1,500 cycles • 2.0 x capacity of SLC • 45 nm MLC has ~ 100 electrons from level to level • Focus on capacity

  10. From Flash memory to SSD

  11. Typical SSD Block diagram

  12. Typical SSD: What's in the box?? ARM Processor Power Capacitor Flash Gang Host Interface Flash Memory Controller DRAM

  13. Why Solid State Drives?

  14. Why SSD?: Performance

  15. How many 15krpm drives = 1 SSD?Random 8k writes

  16. How many 15krpm drives = 1 SSD?Random 8k reads

  17. Why SSD?: Energy

  18. SSD Power Efficiency Most HDDs and SSDs specify “Active” power No standard definition of what “active” means Analogous to “litres per hour at maximum speed” Only useful comparison if everyone has same maximum speed What matters is IOPS/Watt (Enterprise) or power curve (Client) For enterprise applications measure work done per Watt consumed under a specific workload Analogous to “Km per liter (city)” For client applications measure power for representative usage with standard benchmarks (ie MobileMark, etc) Analogous to “litres per standardized 200-kms road trip”

  19. Cost Effective PerformanceSSDs are 70X more cost effective • Enterprise HDD • 180 Write IOPS • 320 Read IOPS • 300 GB • ~18W • $ per IOPS: 2.43 • IOPS/W: ~14 • Enterprise SSD • 7,000 Write IOPS • 35,000 Read IOPS • 32GB • ~3W • $ per IOPS: 0.04 • IOPS/W: ~7000

  20. Why SSD?: Reliability

  21. SSD Reliability has two parts MTBF Measure of time between failures due to manufacturing or component defects 1.5~2 million hours typical for an enterprise SSD Endurance All SSDs wear out due to data writes Indication of life based on an usage condition Usage conditions vary for consumer and performance products Enterprise SSDs are specified to last several years under predefined usage conditions

  22. Endurance Factors Wear-leveling efficiency Write amplification NAND cycles SSD densities

  23. What's Wear Leveling ? Wear-leveling: a set of algorithms that attempt to maximize the lifetime of flash memory by evening out the use of individual cells.

  24. Sun SSD Strategy and Portfolio

  25. SSD predictions Prediction 1: SSD will be more cost effective in 2009

  26. SSD predictions Prediction 2: SSD will be bigger in capacity in 2015

  27. Where to Store Data?Optimization Trade-Off

  28. Where to deploy SSDs?Storage or Server?

  29. Sun SSD StrategyStep 1 – HDD Replacement

  30. Sun SSD StrategyStep 2 – Lightning Flash Array

  31. ZFS and the Hybrid Storage Pool

  32. ZFS Hybrid Storage PoolsSSDs Accelerate Synchronous Writes ZFS caches blocks in system main memory (DRAM) This cache is called the ZFS Adaptive Replacement Cache (ARC) All synchronous writes go to the ZFS Intent Log (ZIL) before they can complete Database logs, NFS servers ZFS can separate the ZIL onto separate devices (ZFS log devices or slogs) Putting the ZIL on SSDs will greatly accelerate the performance of synchronous writes DRAM SSD HDD

  33. ZFS Hybrid Storage PoolsSSDs Accelerate Reads – ARC & L2ARC Older/least frequently accessed blocks in the ARC have to be evicted for newer data blocks or due to application demands for memory Blocks evicted from the ARC are written into L2ARC On reads, if we miss the ARC we go to the L2ARC If the reads miss the L2ARC we go to disk DRAM SSD HDD

  34. ZFS Hybrid Storage PoolsFaster, Cheaper, Less Power More IOPS Lower $GB Lower Power Consumption Less Rack Space Hybrid Storage Pool Enterprise HDDs SSDs High Capacity HDDs

  35. Thank You!An overview on Hybrid Storage Technologies Paolo Bianco Storage Architect Sun Microsystems 35

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