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Mendocino

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17 years ago

M

Mendocino

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October 12th, 2009 01:00

Disk alignment with thin (virtual) provisioning

Hi,

in the CLARiiON Best Practices for FC Storage the topic "Disk Alignment" is well described.
We are considering the use of virtual provisioning on our new CLARiiON systems. Are disk crossings and disk alignment still issues than?

Thanks!
Best regards
Dieter
  • jps00

    2 Intern

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    Posted October 12th, 2009 06:00

    The short answer is, No. Alignment is a performance optimization. A user choosing and provisioning VP does not have the fine-level of control over the LUN with VP needed to align it.

    If your workload has the I/O profile that would benefit from alignment, and requires a higher-level, and more deterministic performance than available with VP, a traditional RAID group/LUN should be provisioned.
  • Dr.diSousa

    1 Rookie

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    Posted November 1st, 2009 11:00

    And what happened with the Windows 2008 host that doesn't need to align volumes (it's done by the OS itself)?

    Are the thin LUNs aligned?

    Thanks in advance.

    Dario
  • jps00

    2 Intern

    392 Posts

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    Posted November 2nd, 2009 06:00

    Thin LUNs cannot be aligned because of the way storage is incrementally allocated from the pool of available storage. Any alignment performed by a file system will have not effect.

    The whitepaper EMC CLARiiON Virtual Provisioning in its Thin LUNs section describes how storage is allocated. This paper is available on PowerLink.