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We have created few volumes in storage array. Via Iscsi initiator those volume have been added into host machine which is Windows 2012 R2. For few volumes when we delete the contents ,the volume size is not reduced in the storage array side. But the disk content is deleted from host side. In the array side when we verify there is no unmap stats. So we suspect that from host side there is no unmap event is triggered.

How to find whether UNMAP request is raised from windows host? we are checking event viewer, but don't know how to look for UNMAP request. Can some one help?

Samselvaprabu
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What is your SAN manufacturer and model? What kind of disks are attached to SAN itself (SATA or SAS SSD)? Usually, all events related to TRIM/UNMAP can be found inside SAN logs, but Windows itself doesn't record it (only in case needed software from SAN manufacturer is installed).

Strepsils
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    I read that we don't need to run manual retrim command in order to raise UNMAP request from Windows 2012 onwards. I am just deleting contents and not issuing retrim commands. Will it be an issue? – Samselvaprabu Feb 11 '19 at 10:41
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    It is true. The OS will optimize and reclaim storage space (TRIM/UNMAP) automatically after files removal. SAN along with Disks itself should support TRIM/UNMAP technology – Strepsils Feb 12 '19 at 11:42