Topic
  • 7 replies
  • Latest Post - ‏2012-09-04T14:12:51Z by SriramIyer-StorageSSR
bio1975
bio1975
7 Posts

Pinned topic Add MDISK to storagepool with volume

‏2012-02-09T21:31:49Z |
Hi
I added a enclosure in my V7000 right now i want to expand my storage pool (the HD are all the same size) of mdisk adding us. My question is as follows:
Since volumes previously created on the storage pool used for all extents of mdisk now with the addition of other mdisk the extents of the already existing volumes will be spread over all mdisk (old and new), or remain only on the old ones?

Thank you
Fabio
Updated on 2012-09-04T14:12:51Z at 2012-09-04T14:12:51Z by SriramIyer-StorageSSR
  • chriscanto
    chriscanto
    291 Posts

    Re: Add MDISK to storagepool with volume

    ‏2012-02-10T16:22:16Z  
    There is no change to the placement of the extents used for the existing volumes; they will remain on the original set of mdisks in the pool.

    The extents from the new arrays will be used when new volumes are created or existing volumes are expanded.
  • TadSmith
    TadSmith
    46 Posts

    Re: Add MDISK to storagepool with volume

    ‏2012-02-10T16:56:35Z  
    There is no change to the placement of the extents used for the existing volumes; they will remain on the original set of mdisks in the pool.

    The extents from the new arrays will be used when new volumes are created or existing volumes are expanded.
    To follow up then, adding mdisks to a storage pool after volumes are created will not help spread the performance load over more disk spindles? It will only allow for additional space? For maximum performance, we should have all of the available mdisks in the storage pool prior to creating any volumes?
  • SystemAdmin
    SystemAdmin
    4779 Posts

    Re: Add MDISK to storagepool with volume

    ‏2012-02-10T17:17:48Z  
    • TadSmith
    • ‏2012-02-10T16:56:35Z
    To follow up then, adding mdisks to a storage pool after volumes are created will not help spread the performance load over more disk spindles? It will only allow for additional space? For maximum performance, we should have all of the available mdisks in the storage pool prior to creating any volumes?
    Hi,

    You analysis is correct, but there is a trick you can use.

    The SVCTools package which is available on developerworks

    https://www.ibm.com/developerworks/mydeveloperworks/groups/service/html/communityview?communityUuid=5cca19c3-f039-4e00-964a-c5934226abc1

    contains a script called balance.pl which will redistribute the data over the new managed disks. At present, a one line change to the published version of the script (documented in the forum below) will make the script work on a V7000

    http://www.ibm.com/developerworks/forums/thread.jspa?threadID=372939

    Hope this helps

    Andrew
  • SriramIyer-StorageSSR
    10 Posts

    Re: Add MDISK to storagepool with volume

    ‏2012-09-03T12:02:24Z  
    Well, i guess with the new firmware 6.4.0.x (in my case) this behavior has changed because i recently added 3 mdisks in my existing storage pool.
    today when i am checking the new "mdisk properties --> dependent volumes" its showing all volumes in the pool.
    i had not created any new volumes in the pool after adding mdisks.
  • SriramIyer-StorageSSR
    10 Posts

    Re: Add MDISK to storagepool with volume

    ‏2012-09-03T13:04:07Z  
    i crosschecked thru CLI as well
    the new mdisks report positive values in "no_of_extents" column for lsmdiskextent command
  • SystemAdmin
    SystemAdmin
    4779 Posts

    Re: Add MDISK to storagepool with volume

    ‏2012-09-04T13:01:14Z  
    i crosschecked thru CLI as well
    the new mdisks report positive values in "no_of_extents" column for lsmdiskextent command
    If your pool/volume have EasyTier enabled, when extends are moved from SSD back to disk, the new mDisks will be used. So over time, the new mdisks will be used without you having to do anything.

    This might explain what you are experiencing.

    /Anders
  • SriramIyer-StorageSSR
    10 Posts

    Re: Add MDISK to storagepool with volume

    ‏2012-09-04T14:12:51Z  
    If your pool/volume have EasyTier enabled, when extends are moved from SSD back to disk, the new mDisks will be used. So over time, the new mdisks will be used without you having to do anything.

    This might explain what you are experiencing.

    /Anders
    Hi Anders

    as rightly pointed out by you my pool does have easy tiering enabled.

    Thanks for the clarity.