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What are Linux host operating system considerations when using SCSI UNMAP with E-Series thin volumes

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Applies to

E-Series Controller Firmware 8.xx

Answer

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.

Red Hat Enterprise Linux Release 6:
Red Hat recommends the use of batch discard operations by running the fstrim command. See section 2.4, 'Discard Unused Blocks,' in the
Red Hat Enterprise Linux 6: Storage Administration Guide

Red Hat Enterprise Linux Release 7:
Red Hat recommends the use of batch discard operations by running the fstrim command. See section 2.4, 'Discard Unused Blocks,' in the Storage Administration Guide.

Red Hat Enterprise Linux Release 8:
Red Hat recommends the use of batch discard operations by running the fstrim command. See Chapter 8. Discarding unused blocks in the Storage Administration Guide.

Red Hat Enterprise Linux Release 9:
Red Hat recommends the use of batch discard operations by running the fstrim command. See Chapter 22. Discarding unused blocks in the Storage Administration Guide.

SUSE Linux Enterprise Server Releases 11 and 12:
The Storage Administration Guide topic 'Freeing Unused Filesystem Blocks' recommends running /sbin/wiper.sh weekly to batch the unmap activity; see SUSE Doc Storage Administration Guide

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