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FW 6.0 EPA, UNMAP and SyncRep
Dear Nashua Gurus,
just got the FW 6.0 EPA and read the Group Admin Guide. This states that it´s recommended to NOT enable SCSI UNMAP when using ESXi 5 if using standard replication. I understand that, because it could cause huge replication ammounts. Now my question would be: Does this recommendation also fits when using SYNCREP? I am asking because with SyncRep EVERY write goes to both pools, thus, if the SCSI UNMAP command is also a write command, it should NOT harm the SYNCREP in my understanding. Am i correct?
Best regards,
Joerg
Anonymous
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July 20th, 2012 12:00
From the v6 Release notes: Same goes for SYNC Rep volumes, don't use UNMAP.
Unmapping and Replicated Volumes
It is not advisable to run operations that result in SCSI unmap operations (for example, format or defrag) on volumes on which replication (including Synchronous Replication) is enabled.
Such operations on replicated volumes result in zeros being written to the destination sectors of the volume. This writing of zeros can cause the operations to take a very long time to complete, and no space is reclaimed. Therefore, Dell recommends that you disable unmapping on hosts or volumes (depending on the host operating system) that are using replicated volumes. Refer to the following sections for information on disabling and enabling unmapping in VMware ESX, Red Hat Enterprise Linux, or Windows 8/Windows Server 2012 operating systems.
joergriether
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July 20th, 2012 13:00
thanks, Don.
Best regards,
Joerg
Anonymous
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July 20th, 2012 13:00
You are most welcome. Have a great weekend!
FamousRuler
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July 3rd, 2013 07:00
Hi,
just an addition to this.. If I pause SYNCREP and then execute the UNMAP command on ESXi 5.1, will this be ok? Or do I need to disable SYNCREP instead of just pause it?
Anonymous
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July 3rd, 2013 07:00
Hello,
No. You would have to delete the replication, pausing or disabling wouldn't be enough. Then re-do it. But over time you'd have to do it again and again.