Energy efficient storage in vm

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Energy efficient storage in vm

  1. 1. Energy-Efficient Storage in Virtual Machine Environments Lei Ye, Gen Lu, Sushanth Kumar, Chris Gniady, John H. Hartman Department of Computer Science University of Arizona
  2. 2. Energy is Critical App App App App App App … … … OS1 OSn OS1 OSn OS1 OSn VMM VMM VMM  Energy consideration is critical for system design  Virtualization is becoming common in all platforms  Integration of virtualization and energy management is critical for overall system efficiency Xen Summit at AMD April 28-29, 2010 1
  3. 3. Current Environment for Energy Management Applications Operating Systems Physical Hardware  OS is the central point for energy management  Global views of application execution  OS directly interacts with the hardware  Detailed hardware knowledge allows sophisticated energy management Xen Summit at AMD April 28-29, 2010 2
  4. 4. Abstraction in Virtual Machines Virtual Machine Monitor  Where should we manage energy?  OS only sees the virtualized hardware  VMM is unaware of the application execution  Separation of hardware and OS makes energy management a challenge Xen Summit at AMD April 28-29, 2010 3
  5. 5. Cross-layer Energy Optimization  Goals  Preserve VM abstractions  Adapt current energy optimization  Approach  Shape I/O accesses at VMM  Provide hints from VMM to the VMs  Outcome  Integrate existing disk energy management into VM Xen Summit at AMD April 28-29, 2010 4
  6. 6. Outline  Introduction  Existing Mechanisms  Design  Evaluation  Conclusion Xen Summit at AMD April 28-29, 2010 5
  7. 7. Existing Disk Energy Management Last I/O New I/O Spin-down I/O Idle sleep I/O Spin-up Timeout Timeout starts expires  Goal: Maximize length of sleeping periods  Must exceed break-even time  Approach: Shaping write activities  Consequence:  Maximize disk off time  Reduce disk spin-ups Xen Summit at AMD April 28-29, 2010 6
  8. 8. Buffer Cache File Buffer Applications System Cache Linux Kernel  Function  Store data temporarily (default 30 seconds)  Perform data transfer for block device  Advantage  Trade disk accesses for memory accesses  Disadvantage  Loss of buffered data in case of system crash Xen Summit at AMD April 28-29, 2010 7
  9. 9. Buffer Cache Complicates Timeout App I/O Buffer cache Data delivered to buffer cache flush to disk 30 seconds I/O Idle Idle sleep I/O Spin-up Timeout Timeout starts expires  Timeout might occur when there are pending writes  Disk spin-up might occur even in absence of application I/O Xen Summit at AMD April 28-29, 2010 8
  10. 10. Early Flush OS I/O Idle Buffer Flush Idle Idle Idle Early Flush Physical Disk state I/O Idle I/O sleep  Do buffer flushes prior to shutdown  No impact on desired I/O reliability Xen Summit at AMD April 28-29, 2010 9
  11. 11. Extended Buffering OS Idle Buffer Flush Idle Idle Buffer Flush I/O Idle 30 seconds Physical Buffer being flushed Disk state sleep sleep I/O sleep Extended idle time  Can extend idle time under writes  May impact I/O reliability Xen Summit at AMD April 28-29, 2010 10
  12. 12. Buffer Flushes in Virtual Machines VM1 I/O Idle Idle Buffer Flush Idle Idle IdleIdle VM2 I/O Idle I/O Idle Buffer Flush Idle Virtual Machine Monitor Physical Disk state I/O Idle I/O Idle I/O Idle sleep sleep sleep  Guest OS is unaware of physical disk state  Buffer flushes from VMs are unsynchronized Xen Summit at AMD April 28-29, 2010 11
  13. 13. Early Flush in Virtual Machines VM1 I/O Idle Idle Buffer Flush Idle Idle Idle Idle Idle VM2 I/O Idle Buffer Flush Idle Idle Idle Early Flush Notification Virtual Machine Monitor Physical Disk state I/O Idle I/O sleep  Hints signal disk shutdown and trigger flush  Disk spin-ups avoided and disk idle time maximized Xen Summit at AMD April 28-29, 2010 12
  14. 14. Buffering in Virtual Machine Monitor  Extend disk idle time  Buffer writes from VMs  Only when the disk is sleeping  Only one copy of data  Buffer is flushed when:  VMM buffer timeout (30 seconds)  Read request from a VM  Reads and sync from VMs are processed immediately  Impact I/O reliability Xen Summit at AMD April 28-29, 2010 13
  15. 15. Evaluation Methodology  Trace collection  8 concurrent VMs as remote desktops on Xen  Users interact with VMs remotely via VNC  Rsyslog: timestamps of I/O activity, I/O type, access size, domain identifier, process identifier, process name, and file inode  Traces: 12 hours per VM  Common interactive applications  Disk drive:  WD2500JD: High performance drive, 9 s. long spin-up time Xen Summit at AMD April 28-29, 2010 14
  16. 16. Disk I/O Trace Statistics Number of Number of Number of Number of Total Idle VMs Reads Writes Idle Periods Time [s] 1 62951 1339 255 40071 2 64886 17031 435 37470 4 83050 59407 601 31263 8 160049 103840 566 20450  Configuration  1 VM – 1 user  2 VMs – 2 concurrent users  4 VMs – 4 concurrent users  8 VMs – 8 concurrent users Xen Summit at AMD April 28-29, 2010 15
  17. 17. Distribution of Idle Periods 1 VM 2 VMs 4 VMs 8 VMs 700 600 Number of Idle Periods 500 400 300 200 100 0 2 4 8 16 32 64 128 Time [Break-Even Period] Xen Summit at AMD April 28-29, 2010 16
  18. 18. Energy Consumption S-Standard, B-Buffering, F-Early Flush, BF-Buffering&Early Flush 500 Sleep Energy Consumption (KJoules) 400 Power-Cycle Active 300 200 100 0 S B F BF S B F BF S B F BF S B F BF 1 VM 2 VMs 4 VMs 8 VMs Xen Summit at AMD April 28-29, 2010 17
  19. 19. Execution Time S-Standard, B-Buffering, F-Early Flush, BF-Buffering&Early Flush 14 Spin-up Idle > BE Active 12 Execution Time (Hours) 10 8 6 4 2 0 S B F BF S B F BF S B F BF S B F BF 1 VM 2 VMs 4 VMs 8 VMs Xen Summit at AMD April 28-29, 2010 18
  20. 20. Reducing Spin-ups S-Standard, B-Buffering, F-Early Flush, BF-Buffering&Early Flush 600 Buffered Write 500 Write Number of Spin-ups 400 Read 300 200 100 0 S B F BF S B F BF S B F BF S B F BF 1 VM 2 VMs 4 VMs 8 VMs Xen Summit at AMD April 28-29, 2010 19
  21. 21. Energy Delay Product S-Standard, B-Buffering, F-Early Flush, BF-Buffering&Early Flush 1.2 Normalized Energy Delay Product 1 0.8 0.6 0.4 0.2 0 S B F BF S B F BF S B F BF S B F BF 1 VM 2 VMs 4 VMs 8 VMs Xen Summit at AMD April 28-29, 2010 20
  22. 22. Buffering in VMM with Immediate Sleep VM1 Idle Buffer Flush Idle VM2 Writes being buffered Idle Buffer Flush Idle VMM Writes being buffered Delayed Writes Physical 30 seconds Buffer being flushed Disk state sleep sleep I/O sleep Extended idle time  The disk is put to sleep immediately after a buffer flush  VMM buffer flush independent from VM I/Os Xen Summit at AMD April 28-29, 2010 21
  23. 23. Immediate Sleep Optimization B-Buffering, BF-Buffering&Early Flush, T-Timeout, I-Immediate 400 Energy Consumption (KJoules) Sleep 300 Power-Cycle Active 200 100 0 T I T I T I T I T I T I T I T I B BF B BF B BF B BF 1 VM 2 VMs 4 VMs 8 VMs Xen Summit at AMD April 28-29, 2010 22
  24. 24. Writes in Buffering and Early Flush VMs Mechanisms Write Delay Delayed Writes Early Flush Participants 1 Buffering 14.5s 3.5 N/A Early Flush N/A N/A 1.0 Buffering & Early Flush 10.6s 1.9 1.0 2 Buffering 13.8s 8.3 N/A Early Flush N/A N/A 1.1 Buffering & Early Flush 14.0s 9.2 1.0 4 Buffering 13.8s 11.3 N/A Early Flush N/A N/A 1.2 Buffering & Early Flush 15.5s 9.8 1.2 8 Buffering 13.9s 14.1 N/A Early Flush N/A N/A 1.4 Buffering & Early Flush 13.2s 16.1 1.5  Buffering in the VMM can result in additional delays  The longer the write resides the buffer, the higher the impact on reliability Xen Summit at AMD April 28-29, 2010 23
  25. 25. Conclusion  Existing energy optimizations require modification to be effective in a VM environment  OS only sees the virtualized hardware  VMM is unaware of the application execution  Early Flush reduces spin-ups due to buffer flushes  Reduce energy by 10.5% compared with standard case in 8 VMs  VMM buffering extends disk idle time by delaying VM writes  Reduce energy by 7.7% compared with standard case in 8 VMs  Combination reduces energy consumption by 14.8% in 8 VMs Xen Summit at AMD April 28-29, 2010 24
  26. 26. Q&A Thank You Xen Summit at AMD April 28-29, 2010 25

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