Which file systems support UNMAP on a Linux server connected to an XtremlO cluster?

The UNMAP command, also known as TRIM, allows a host file system to notify a storage array, like Dell XtremIO, that specific blocks are no longer in use and can be reclaimed. This is crucial for the efficiency of thin-provisioned LUNs. On Linux servers, modern file systems are required to support this functionality. Ext4 and XFS are the most common enterprise Linux file systems that have robust support for UNMAP, either through the discard mount option or the fstrim utility. ZFS on Linux also provides this capability through the autotrim pool property. Older file systems such as Ext3 and ReiserFS do not have native support for the UNMAP command.

A. Ext3 does not natively support the UNMAP command, which was introduced in its successor, Ext4.
B. ReiserFS (specifically the widely used version 3) lacks native support for the UNMAP command.
D. Both ReiserFS and Ext3 are older file systems that do not support the UNMAP command.

1. Dell EMC XtremIO Storage Array Version 4.0 and higher Host Configuration Guide: In the "Linux settings" section under "Linux space reclamation," the guide states, "The ext4 and xfs file systems support the discard option, which issues TRIM/UNMAP commands in real time..." This document confirms support for Ext4 and XFS. (Reference typically found in Chapter 4: Linux Host Configuration).

2. Red Hat Enterprise Linux 8 Documentation, Managing file systems, Section 2.10. Discarding unused blocks: "The XFS and ext4 file systems support the discard operation... Red Hat Enterprise Linux 8 supports batch discard operations on XFS and ext4 file systems with the fstrim utility." This official vendor documentation confirms support for Ext4 and XFS and makes no mention of Ext3.

3. OpenZFS Documentation, zpoolprops(7) Manual Page: The autotrim property is described as follows: "If set to on, ZFS will periodically issue TRIM/UNMAP commands for all free space in the pool. This allows block-reclaim-capable hardware to reclaim unused blocks." This confirms UNMAP support for the ZFS file system.