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The Impact of Logical and Physical Fragmentation in a Virtual Environment

The Impact of Logical and Physical Fragmentation in a Virtual Environment. Presented by Raxco Software, Inc. February, 2010. What The Experts Say. “.

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The Impact of Logical and Physical Fragmentation in a Virtual Environment

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  1. The Impact of Logical and Physical Fragmentation in a Virtual Environment Presented by Raxco Software, Inc. February, 2010

  2. What The Experts Say “ Like physical disk drives, virtual disks can become fragmented. Defragmenting disks rearranges files, programs and unused space on the virtual disk so that programs run faster and files open more quickly.” VMware Defragmenting Virtual Disks http://www.vmware.com/support/ws55/doc/ws_performance_defrag.html

  3. Experts… “ Performance in Windows guest operating systems may also be affected by disk fragmentation” VMware ACE https://www.vmware.com/support/ace/doc/disks_ntperf_ace.html

  4. Experts… “ • The two biggest reasons I see virtual machines get slower over time is due to: • incorrect virtual machine additions • installed and (2) disk fragmentation.” • Andrew Connell • Former MS Share Point Developer • Microsoft MVP-Content Management Server

  5. What is Fragmentation? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

  6. Sample Fragmentation Problems • 10-15 minutes to launch Notes • Users locked out of servers • Servers won’t boot • Application hangs and crashes • System errors due to metadata fragmentation • Video/audio “flickers” • Prolonged backup

  7. Cost of Fragmentation • Productivity • Support • Unnecessary hardware • Longer backups • Opportunity

  8. The Fragmentation Issue • Logical fragmentation • Physical fragmentation • File fragmentation • Free space fragmentation

  9. The Logical Level • To format a partition Windows needs to know if it is NTFS/FAT, cluster size and disk size • Bitmap file is how NTFS “sees” the disk • Cannot distinguish between physical disk types • MFT is created along with metadata files NTFS

  10. File Allocation • Create MFT record (one or more) • Bitmap accessed to locate free space • MFT record is updated with content • NTFS passes LCN’s to disk driver LCN’s to Disk Driver Bitmap Access MFT Update Create

  11. Anatomy of the MFT (vcn, lcn, run length): (8a85, 9189a, 7)

  12. File Access • Load portion of MFT with correct record via directory • Locate file in the MFT • Pass starting LCN and run length to disk controller • Number of physical disk seeks determined by the number of logical fragments # Physical Seeks Locate File # LCN’s Load

  13. Wasted Seeks

  14. NTFS Expert Concludes… • Free space fragmentation slows down writes • Free space fragmentation blocks on write • File and free space fragmentation causes needless seeks • Slower the disk the greater the bottleneck

  15. The Physical Level • NTFS reports starting LCN and length to the disk controller • Disk controller maps LCN to PCN based on its software/firmware • Data written to disk

  16. File Fragmentation and Free Space • Data files — most numerous • System files — Page file and hibernate file • Metadata files — $logfile, $bitmap, $badclus • Free space — the real enemy!

  17. Fragmentation and VM’s • Windows guests have all the same NTFS behavior • Resource contention between Windows guests • Resource contention between guests and the host (Hyper-V and vSphere) • Free space fragmentation not good for dynamic vmdk, vhd

  18. Possible Solutions • More hardware • Windows Defragmenter – not enterprise solution • Perfect Disk vSphere Bundle • Perfect Disk Hyper-V Bundle

  19. How Does Defragmentation Help? • File defragmentation speeds up disk reads • Free space defragmentation speeds up disk writes • Reduces unnecessary physical disk seeks • Reduces resource contention for VM’s • Fastest possible logical and physical I/O

  20. No Virtual Awareness Virtual Machine and Status VM1 Idle VM1 Idle VM1 Busy VM1 Busy Basic Automatic Defragmentation Defrag Status 0 Remaining Resources (CPU & I/O) For Busy Machines 100

  21. Virtualization Awareness Virtual Machine and Status VM1 Idle VM1 Idle VM1 Busy VM1 Busy Automatic Defragmentation with Virtualization Awareness Dynamic Monitor Defrag Status 0 Remaining Resources (CPU & I/O) For Busy Machines 100

  22. PerfectDisk Virtual Solutions • Virtually Aware for vSphere and Hyper-V • vSphereconsole snap-in • Enterprise console for Hyper-V • Host & Guest solutions for Hyper-V • Support for vMotion and Live Migration • Fully automated compaction for Hyper-V • Automated shrink & re-indexing for VMware Workstation

  23. Win a Free PerfectDisk Virtualization Bundle Today! Just Register. • For more information: • Ask a question • See me after this presentation • Go to www.perfectdisk.com

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