Primary Storage

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  • 1.  FCM behind SVC releasing capacity?

    Posted 27 days ago
    We've gone through a set of actions in one of our test environments whereby we can't make sense of what the capacity reporting that the SVC and backend FCM arrays are showing. To describe our environment:
    • Front end SVC cluster, running 8.3.1.3 code
    • Backend FCM storage running 8.4.0.4 code
    • Backend HDD storage running 8.3.1.3 code
    On the SVC I did the following:
    • Moved LUN's from dedicated FCM mdiskgrp to dedicated HDD mdiskgrp
    • When I checked the mdiskgrp on the SVC, it went down the balance of the LUN's moved, as expected
    • But when I check the backend FCM storage array there was no change in usable capacity stats for it's storage pool
    The LUN's that moved back to disk storage pool, according to SVC, have a very low compression rate, so I would have expected the FCM storage usable capacity to go down also. Is there some sort of cleanup that needs to occur on the FCM array to allow this data which has moved to be reclaimed, or something like that?

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    Andy 91717
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  • 2.  RE: FCM behind SVC releasing capacity?

    IBM Champion
    Posted 27 days ago
    you need to check backend unmap settings on SVC and backend FCM storage ( lssystem | grep unmap )  
    you will find more information on Performance and Best Practices Guide for IBM Spectrum Virtualize 8.5 Redbook starting in Chapter 3.3.2  https://www.redbooks.ibm.com/abstracts/sg248521.html

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    Nezih Boyacioglu
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