1 / 37

ENERGY-EFFICIENCY AND STORAGE FLEXIBILITY IN THE BLUE FILE SYSTEM

ENERGY-EFFICIENCY AND STORAGE FLEXIBILITY IN THE BLUE FILE SYSTEM. E. B. Nightingale and J. Flinn University of Michigan. Key ideas. Reduce power consumption of portable devices Two big culprits Disk drive Wireless Integrate flash drives. Dynamic storage hierarchy.

rikerj
Download Presentation

ENERGY-EFFICIENCY AND STORAGE FLEXIBILITY IN THE BLUE FILE SYSTEM

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ENERGY-EFFICIENCY AND STORAGE FLEXIBILITYIN THE BLUE FILE SYSTEM E. B. Nightingale and J. Flinn University of Michigan

  2. Key ideas • Reduce power consumption of portable devices • Two big culprits • Disk drive • Wireless • Integrate flash drives

  3. Dynamic storage hierarchy • We should power down drives when they are idle • But this causes powering up delays • To mask these delays introduce a dynamic storage hierarchy • Includes flash drives and remote server • Takes into consideration state of local disk drive

  4. Disk is powered up Disk is powered down Flash Flash Server Disk Disk Server Examples The storage hierarchy depends on the status of the hard disk.

  5. Incorporating flash drives • To satisfy read requests, Blue FS looks first in the flash drive • Implies • A write all/read any policy • Treating flash drives as caches • Need a quick way to query flash drive contents

  6. More on caches • Unit of caching is block • Can cache some blocks of a file but not all • Must maintain information on validity and currency of each cached block • See details in paper

  7. Write to all/read any • All writes are propagated to all devices Server Disk

  8. Advantages • Write all allows read any • Future power savings • Requires efficient writes • Propagates all updates to the server • Unless in disconnected mode

  9. Aggregating writes (I) • Blue FS maintains one write queue per device Server Disk

  10. Aggregating writes (II) • When it writes to a device, it flushes the whole queue Server Disk

  11. Aggregating writes (III) • After the writes, each queue is empty Server Disk

  12. More on device queues • Device queues share among themselves all common blocks • Save space • Blocks in device queues can be accessed through a hashing scheme • Always access most recent version of a block even when it is not yet saved on any device

  13. Why? • Makes a lot of sense for disk drive and remote server • Power up disk, do a few updates, then power down • Power up wireless connection, send a few updates then power down • Delaying updates allows BlueFS to coalesce multiple updates to the same block

  14. Using flash drives as caches • Small flash drives cannot contain whole contents of file system • Especially true in 2004! • Must have a fast way to find whether a file is cached or not • Enode

  15. E-node • Captures all the information Blue FS has about the validity of an object • E-nodes are • Hashed by file id • Stored in an e-node cache managed by LRU replacement policy • Default size is one MB

  16. Cache consistency • Uses • Optimistic replica control (Coda) • Callbacks (AFS) • Changes • Blue FS maintains callbacks on a per-device basis, instead of on a per-client basis • Server queues invalidation messages when a device is disconnected.

  17. Updated for Fall 2012 Optimistic replication • Optimistic replication control protocols allow access in disconnected mode • Tolerate temporary inconsistencies • Promise to detect them later • Provide much higher data availability Optimistic replication control putsdata availability above data consistency

  18. Updated for Fall 2012 Callbacks (I) • When a client opens a file for the first time, server promises to notify it whenever it receives a new version of the file from any other client • Promise is called a callback • Relieves the server from having to answer a call from the client every time the file is opened • Significant reduction of server workload

  19. If machines could talk (I) 99% of these requests are useless! I should contact the server each time I open any file Server Client

  20. If machines could talk (II) You do not need to call me: I promise to call you back if anyone has modified the file ?? Server Client

  21. If machines could talk (III) What if I do not receive your callback? Though luck! Server Client

  22. Callbacks (II) • Callbacks can be lost! • Client will call the server every tauminutes to check whether it received all callbacks it should have received • Cached copy is only guaranteed to reflect the state of the server copy up totau minutes before the time the client opened the file for the last time

  23. If machines could talk (IV) Sure as long as you do not do it too frequently I will contact you from time to time to check for lost callbacks Server Client

  24. Disconnected mode • Like Coda, Blue FS works in disconnected mode • User has access to all files cached • On local disk drive • On flash drive if any • Can even specify that some files must always be cached • Affinity

  25. Disconnected mode (II) • When a device is disconnected, server queues all callbacks that could not be delivered to the device • Speeds up reintegration • If inconsistencies are discovered at reconnection time, will run a resynchronization process

  26. Accessing large files • When disk is powered down, Blue FS get first file blocks from remote server

  27. Deciding which device to use • If decisions are made for each individual access • Will never activate a disk that’s powered down • Blue FS uses ghost hints • Measure penalty for not using a disk that is powered down for a given access • When sum of ghosts hints exceeds the cost of powering up the disk, disk is powered up

  28. Updated for Fall 2012 Applications Wolverine To BlueFS Server Up-call VFS Operations LinuxFile Cache BlueFSKernel Module USBStick CardFlash Micro-drive Local Disk LinuxKernel Blue FS architecture (II)

  29. Blue FS architecture (I) • Most of Blue FS functionality is implemented in a user-level process • Wolverine • Kernel-resident part of Blue FS intercepts I/O calls that have to be forwarded to Wolverine

  30. Applications Wolverine To BlueFS Server Up-call VFS Operations LinuxFile Cache BlueFSKernel Module USBStick CardFlash Micro-drive Local Disk LinuxKernel Blue FS architecture (II)

  31. Performance • Will use a standard benchmark • Andrews/AFS benchmark • Will compare interactive delays andpower consumption against • NFS • Coda with synchronous server updates (Coda) • Coda with asynchronous server updates(Coda WD)

  32. Interactive delay 6000.0 Ten times faster than NFS, 16% faster than Coda WD

  33. Adding a 16MB flash drive • Assumes that cache is fully loaded • 48% shorter interactive delay 48%, 25% less energy

  34. Energy efficiency • Different benchmark run with half-full cache • 76% shorter interactive delay, 55% less energy than Coda

  35. Adding a 16MB flash drive • Assumes that cache is fully loaded • 48% shorter interactive delay, 25% less energy

  36. Discussion • Comparison with NFS is unfair • NFS was designed for LANs, not WANs! • Comparison with Coda is fair but • Coda did not incorporate flash drives • Did not exist then! • Coda did not try to minimize power consumption • Portable devices did not exist then!

  37. Conclusion • Blue FS updates Coda by taking into consideration the arrival of • Wireless networks (near ubiquitous access) • Portable devices (limited autonomy) • Flash drives • Retains Coda features such as optimisticreplication, callbacks and disconnected mode operation

More Related