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1 Reply Latest reply: May 16, 2012 11:52 AM by Nik RSS

7420 & iSCSI or FC lun disk space?

eli101 Newbie
Currently Being Moderated
I noticed an issue on iSCSI or FC luns.

We have many configured iSCSI and FC lun's, mostly used with windows servers. by removing files or directory's in windows no disk space gets freed up.

I tried goggling this issue and it appears that blocks are freed but the storage doesn't know about this, causing to never get back the free blocks (disk space), I also found in one of the forums talking about something called "iSCSI unmap" which apparently fixes this issue.

Question: Is this a known issue? What can we do not to run to this issue? or will this issue be addressed at a latter update?

Thanks,
-Eli
  • 1. Re: 7420 & iSCSI or FC lun disk space?
    Nik Expert
    Currently Being Moderated
    Hi.
    It's not bug, it's normal behavior.

    File system generaly do not say to device that this block now free and can be cleare, so LUN ( array) must store all information that was writen on it.

    Some FS can do it. For this use SCSI UNMAP commands. Example of this FS: ext4, NTFS ( from WIN2008 R2).
    Latest revision of Vmware.


    Comstar have this features under ZFS

    http://gdamore.blogspot.com/2011/03/comstar-and-scsi-unmap.html


    I can't find information that Oracle introduce this features.


    Regards.

    Edited by: Nik on 16.05.2012 11:46

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