Lets Design, Implement and do Administration of ESX3

Virtualization with VMWare Infrastructure 3.0

What are Thin Disks,Thick Disks

Posted by Preetam on September 13, 2008

Excellent explanation of various storage technologies, especially Thin disks from vmmba.

 There are three main technologies that can accomplish storage oversubscription:

  1. Linked clones
    • This feature is available in VMware Lab Manager and VMware Workstation at the virtual disk level.  When a linked clone is used, the new VM uses pointers to the original VM for all common data.
    • The additional advantage of linked clones is that whitespace is not stored – for example if an empty data disk is part of a clone operation, the new disk will act as a "thin" disk and only consume the storage that it really requires for data
    • Linked clones can also be accomplished at the datastore level using technologies such as NetApp FlexClone (useful when cloning many VMs at once)
    • Keep in mind: linked clones pay a performance penalty on write operations (using copy-on-write), and put added stress on the source disks on read operations
  2. Thin Disks
    • Thin-provisioned disks are virtual disks that "appear" to the VM as one size, but only consume up to the amount of data that is required by that disk.  So, a 10 GB drive that is 50% utilized will only store 5 GB on disk (a traditional "thick" virtual disk would consume the entire 10 GB on disk)
    • Thin disks are options in VMware Workstation, and are the default disk type when using NFS storage in VMware ESX Server – however, VMs cloned from templates are always thick
    • Storage vendors such as Hitachi and NetApp have LUN-level thin provisioning, but that would only apply to VMware if using RDMs
  3. Deduplication
    • Deduplication is a technology similar to memory page sharing (above), where common data is stored only once.  It is done "after the fact" (ex poste), meaning de-duplication opportunities are scanned using a background process
    • Deduplication is primarily used for backups (e.g. Symantec PureDisk, EMC Avamar, or Quantum DXi-Series), but can also be used on the filesystem itself (today, using NetApp Deduplication, formerly A-SIS)

REFERENCE: www.vmmba.com

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One Response to “What are Thin Disks,Thick Disks”

  1. [...] Originally Posted by manuadoor What is "Thin Disk"?? What are Thin Disks,Thick Disks Lets Design, Implement and do Administration of ESX3 [...]

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