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What are VMware considerations when using SCSI UNMAP with E-Series thin volumes?

Last Updated:


Applies to

E-Series Controller Firmware 8.xx


When you create a thin volume using 08.25.05 or later, it will be recognized as thin by host operating systems that support UNMAP. UNMAP is a SCSI command that can be issued to the storage array by a host system to reclaim space on a thin volume after disk blocks have been deleted by an application or OS. Note that thin provisioned volumes may have been created with earlier versions than 08.25.05, but they will not be reported to the host operating system as thin volumes.

Note: For the procedure to enable thin reporting on legacy volumes after you have upgraded to 08.25.05 or later, see article: How to enable UNMAP on existing Thin Volumes for VMware ESXi

Under VMware, space reclamation is already defined to be a manual activity to minimize performance impact, so no intervention to change defaults is needed. The following VMware knowledge base article describes how to reclaim space in vSphere 5.5 and 6.0 using an esxcli command:
VMware KB: Using esxcli in vSphere 5.5 and 6.0 to reclaim VMFS deleted blocks on thin-provisioned LUNs (2057513) (If you are using VMFS6 in ESXI 6.5, This article is not applicable)

Earlier versions of vSphere use a different CLI command for reclamation. Currently, the earliest VMware ESXi version supported by SANtricity OS 8.25 is 5.1 U3.  The following is a VMware knowledge base article describing the use of vmkfstools and also how to confirm that UNMAP is supported on a LUN.
VMware KB: Using vmkfstools to reclaim VMFS deleted blocks on thin-provisioned LUNs (2014849)

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