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GPFS and SAN

  • 1.  GPFS and SAN

    Posted Tue March 12, 2019 04:45 PM
    Edited by Chandhra Vadlamudi Tue March 12, 2019 05:37 PM
    Hi,

    To mount an external SAN on IIAS, we must first trigger storage_setup
    script which converts SAN lun(s) into GPFS NSD.

    For example, I've performed backups onto mounted SAN and we had an
    issue with GPFS on the appliance and lost GPFS.

    Will we lose the data on the appliance only or the data on the
    appliance + data that was backed up on to the SAN file system as well?



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    Chandhra Vadlamudi
    Lead Datawarehouse DBA
    Blue Shield of CA
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  • 2.  RE: GPFS and SAN

    Posted Wed March 13, 2019 06:21 AM
    You would have to review the script (likely in python). If it starts by destroying any partitions then this is a razing a old building to put up a new one. Then nothing is left on the disks backup and data will be gone. If they aren't that aggressive they may just try to create new partitions with whatever space is left. So its all in the approach.

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    frank pantaleo
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  • 3.  RE: GPFS and SAN

    Posted Thu March 14, 2019 12:41 PM
    Thanks Frank, the script starts saying "Beginning GPFS network disk configuration... This step will format all external luns, a DESTRUCTIVE operation. Proceed? [n|y]y... Converting SAN lun(s) into GPFS NSD..."

    Considering that, I have a scenario:

    1. The SAN has been mounted on IIAS as shown in https://www.ibm.com/support/knowledgecenter/en/SS6NHC/com.ibm.swg.im.iias.admin.doc/doc/appl_SAN_add.html which converts SAN lun(s) into GPFS NSD.
    2. We performed backups to it.
    3. Due to some reason (GPFS issue or software upgrade rollback) the IIAS has to be reinitialized.
    4. Can we still use the backups performed in step2 to restore back?


    ------------------------------
    Chandhra Vadlamudi Lead Datawarehouse DBA
    Lead Datawarehouse DBA
    Blue Shield of CA
    ------------------------------



  • 4.  RE: GPFS and SAN

    Posted Thu March 14, 2019 01:02 PM
    I know that GPFS puts its backups/snapshots into a hidden directory BUT if its getting initialized it may all go away (very likely). The issue you will have with Snapshots is they can't be moved off (using tar for example). So I'm not sure what alternative you have.

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    frank pantaleo
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  • 5.  RE: GPFS and SAN

    Posted Thu March 14, 2019 01:26 PM
    Thank you very much, Frank!

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    Chandhra Vadlamudi Lead Datawarehouse DBA
    Lead Datawarehouse DBA
    Blue Shield of CA
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  • 6.  RE: GPFS and SAN

    Posted Thu March 14, 2019 01:31 PM
    Conceptually, GPFS is a type of file system formats and when we mount an external SAN storage to IIAS appliance, the SAN storage is formatted as a GPFS file system. As result of the re-formatting,  the content/files of this SAN storage may not be readable from out side of the IIAS, where the term GPFS is not relevant. This is what I am understanding.

    However, re-initializing a IIAS appliance should not impact the content of the external SAN storage, even it is a GPFS file system, otherwise, this should be a bug in IIAS.

    Can anyone please correct me if I am wrong?

    Thanks,
    Daniel



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    Daniel Wang
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  • 7.  RE: GPFS and SAN

    Posted Thu March 14, 2019 02:07 PM
    In PDA, we can restore backups performed by one PDA on to another. Where as in IIAS, we can't restore backups performed by one IIAS appliance onto another. 
    At least, we should be able to recover the data from backups incase IIAS reinitializes but that seems to be hard from what Frank mentioned.

    ------------------------------
    Chandhra Vadlamudi Lead Datawarehouse DBA
    Lead Datawarehouse DBA
    Blue Shield of CA
    ------------------------------



  • 8.  RE: GPFS and SAN

    Posted Thu March 14, 2019 02:10 PM
    I would also like to know that if I would like to preserve the content of my external SAN LUNs, which is not GPFS ready yet, I should not mount it to the IIAS appliance at all!

    Can someone please confirm this with me?

    Thanks,
    Daniel

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    Daniel Wang
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