1 / 61

DADA – Dynamic Allocation of Disk Area

DADA – Dynamic Allocation of Disk Area. Jayaram Bobba Vivek Shrivastava. Outline. Introduction Existing Framework Implementation Issues Results Conclusions. Problem. Disk Volumes Allocate physical space on creation Multiple Disk Volumes on a physical disk Unused space

abra
Download Presentation

DADA – Dynamic Allocation of Disk Area

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. DADA – Dynamic Allocation of Disk Area Jayaram Bobba Vivek Shrivastava Department of Computer Sciences, University of Wisconsin Madison

  2. Outline • Introduction • Existing Framework • Implementation • Issues • Results • Conclusions Department of Computer Sciences, University of Wisconsin Madison

  3. Problem • Disk Volumes • Allocate physical space on creation • Multiple Disk Volumes on a physical disk • Unused space • Disk space not a premium • What If? Department of Computer Sciences, University of Wisconsin Madison

  4. Motivation • Virtual Machine Environment • Add Some points • Storage Area Networks • Storage area is the bo • Dynamic Physical Allocation (LFS style) Department of Computer Sciences, University of Wisconsin Madison

  5. Related Work • HP AutoRAID • Dynamically change redundancy levels • Hot Data – Mirrored • Cold Data – RAID 5 • Dynamic migration of data Department of Computer Sciences, University of Wisconsin Madison

  6. Outline • Introduction • Existing Framework • Implementation • Issues • Results • Conclusions Department of Computer Sciences, University of Wisconsin Madison

  7. Existing Framework • Logical Volume Manager (LVM) • User space tool that enables creation of logical volumes of a logical partition. • Supports resizing of volumes. • Device Mapper (DM) • Kernel driver that provides a level of indirection in address translation Department of Computer Sciences, University of Wisconsin Madison

  8. LVM design • Volume Group (VG) • Physical Volume (PV) • Logical Volume (LV) • Physical Extent (PE) • Logical Extent (LE) Department of Computer Sciences, University of Wisconsin Madison

  9. LVM design Physical Device Department of Computer Sciences, University of Wisconsin Madison

  10. LVM design PV PE Department of Computer Sciences, University of Wisconsin Madison

  11. LVM design PV PE Department of Computer Sciences, University of Wisconsin Madison

  12. LVM design LV 1 PV PE Department of Computer Sciences, University of Wisconsin Madison

  13. LVM design LE LV 1 LV2 PV PE Department of Computer Sciences, University of Wisconsin Madison

  14. LVM design LE LV 1 LV2 PV PE Department of Computer Sciences, University of Wisconsin Madison

  15. LVM design LE VG LV 1 LV2 PV PE Department of Computer Sciences, University of Wisconsin Madison

  16. DM design Userspace Applications filesystem interface ioctl interface control interface block interface core device-mapper mapping/target interface linear striped snapshot multipath log kcopyd path selectors hardware handlers round-robin emc Department of Computer Sciences, University of Wisconsin Madison

  17. LVM – DM interaction Device Mapper Kernel Userspace libdevmapper LVM2 Department of Computer Sciences, University of Wisconsin Madison

  18. Outline • Introduction • Existing Framework • Implementation • Issues • Results • Conclusions Department of Computer Sciences, University of Wisconsin Madison

  19. Modifications • A trap mechanism from kernel driver to user-level LVM code. • Support for multiple segments in LV • Support for virtual mappings in driver Department of Computer Sciences, University of Wisconsin Madison

  20. Initial State LVM daemon LVM User space Kernel space Device Mapper Unallocated Disk Space Department of Computer Sciences, University of Wisconsin Madison

  21. Volume Group Creation LVM daemon LVM User space Kernel space Device Mapper PE (4MB) 25 Extents Unallocated Disk Space Department of Computer Sciences, University of Wisconsin Madison

  22. Current Implementation LVM daemon Create LV 32MB User A LVM User space Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  23. Current Implementation LVM daemon User A LVM Map 0-7 extents for user A User space Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  24. Current Implementation LVM daemon User A LVM Map 0-7 extents for user A User space Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  25. Current Implementation LVM daemon User A LVM Create LV User B 16 MB User space Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  26. Current Implementation LVM daemon User A LVM Create LV User B 16 MB map 8-11 extents for B User space Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  27. Current Implementation LVM daemon User A LVM User B map 8-11 extents for B User space Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  28. Current Implementation LVM daemon User A LVM User B Read/write User space Read/write Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  29. Volume Group Creation LVM daemon LVM User space Kernel space Device Mapper PE (4MB) 25 Extents Unallocated Disk Space Department of Computer Sciences, University of Wisconsin Madison

  30. Current Implementation LVM daemon Create LV1 32MB User A LVM User space Kernel space Device Mapper Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  31. Current Implementation LVM daemon User A LVM Virtually map 0-7 extents for user A User space Kernel space Device Mapper {0-7 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  32. Current Implementation LVM daemon User A LVM Create LV User B 16 MB User space Kernel space Device Mapper {0-7 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  33. Current Implementation LVM daemon User A LVM Create LV2 User B 16 MB Virtually map 8-11 extents for B User space Kernel space Device Mapper {0-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  34. Current Implementation LVM daemon User A LVM Write 6MB User B User space Kernel space Device Mapper {0-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  35. Current Implementation LVM daemon User A LVM User B write trap User space Kernel space Device Mapper {0-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  36. Current Implementation On Demand allocation of disk area LVM daemon User A LVM User B write trap User space Kernel space Device Mapper {0-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  37. Current Implementation On Demand allocation of disk area LVM daemon User A LVM Write 6MB User B Allocate 2 extents (8MB) trap User space Kernel space Device Mapper {0-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  38. Current Implementation On Demand allocation of disk area LVM daemon User A LVM Write 6MB User B Allocate 2 extents (8MB) trap User space Kernel space Device Mapper {0-1 linear}{2-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  39. Current Implementation LVM daemon User A LVM User B Write 10MB User space Kernel space Device Mapper {0-1 linear}{2-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  40. Current Implementation LVM daemon User A LVM User B Write 10 MB trap User space Kernel space Device Mapper (0-1 linear}{0-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  41. Current Implementation On Demand allocation of disk area LVM daemon User A LVM User B write trap User space Kernel space Device Mapper {0-7 error} {8-11 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  42. Current Implementation On Demand allocation of disk area LVM daemon User A LVM User B Allocate 3 extents (12 MB) Write 10 MB trap User space Kernel space Device Mapper {0-1 linear}{2-7 error} {11 error} {8-10 linear} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  43. Outline • Introduction • Existing Framework • Implementation • Issues • Results • Conclusions Department of Computer Sciences, University of Wisconsin Madison

  44. Issues • Not the most efficient implementation • On a trap, • How much to allocate? • On demand • Pre-allocate • Where to allocate? • Temporal locality • Spatial locality • Free unused space Department of Computer Sciences, University of Wisconsin Madison

  45. How much? • On-demand • Allocate only as many blocks as needed • Pre-allocate • Pre-allocate physical space for blocks likely to be accessed in the future. • How much? • Where? Department of Computer Sciences, University of Wisconsin Madison

  46. How much? • Tradeoff – Performance vs. Disk Space • Depends on the workload • I/O on critical path • Asynchronous I/O • Multithreaded Applications Department of Computer Sciences, University of Wisconsin Madison

  47. Pre-Allocation Think: Filesystem Block Allocation • Dumb Allocation • Stride Allocation • Multi-Strided Allocation Department of Computer Sciences, University of Wisconsin Madison

  48. Dumb Allocation On Demand allocation of disk area LVM daemon User A LVM Write 6MB Allocate 2 extents (8MB) trap User space Kernel space Device Mapper {0-1 linear}{2-7 error} Free Disk Space Department of Computer Sciences, University of Wisconsin Madison

  49. Stride Allocation On Demand allocation of disk area LVM daemon User A LVM Write 6MB Allocate 4 extents (16MB) trap User space Kernel space Device Mapper {0-1 linear}{2-7 error} Free Disk Space PreAllocated Extent Department of Computer Sciences, University of Wisconsin Madison

  50. Ext2 access pattern Department of Computer Sciences, University of Wisconsin Madison

More Related