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Volume management
29 Dell EMC SC Series: Red Hat Enterprise Linux Best Practices | CML1031
3.8.2 LVM space reclamation and SCSI UNMAP/TRIM
If LVM is used with SC Series volumes, LVM can be configured to respect SCSI UNMAP/TRIM command
recovered space when logical volumes are removed from the member volume group. The space recovered
from this removed logical volume varies depending on whether data reduction is enabled on the SC Series
volumes. This feature applies to RHEL 6 and newer.
To enable the feature, edit the /etc/lvm/lvm.conf file and change the key value pair issue_discards = 0 to
issue_discards = 1.
3.9 Filesystems
The SC Series array supports a wide range of filesystems on Linux. This section focuses on two popular and
stable filesystems: ext4 and xfs. The filesystem can be created on top of a LUN, a LUN partition, or a logical
volume in LVM. Dell EMC recommends using the whole LUN without partition or a logical volume in LVM for
ease of management.
For additional information on supported filesystems and feature limitations, consult the Red Hat Enterprise
Linux Administration Guide on the Red Hat Enterprise Linux Document Portal.
3.9.1 Filesystem label and universally unique identifiers
Filesystem volume labels can be applied when creating a filesystem on the volume or by subsequently using
differing commands. Different filesystems (for example, ext4 or xfs) have different filesystem metadata
schemas and use different commands to view, manage, and change this data.
The Linux operating system generates a universally unique identifier (UUID) for many objects and entities,
including filesystems, on the system. These UUIDs are persistent and do not change. Therefore, they can be
used reliably to reference the various objects including filesystems. The UUID is created automatically during
the filesystem creation.
Create a filesystem and label at the same time:
# mkfs.ext4 -L appfs /dev/sdX #For ext4
# mkfs.xfs -L appfs /dev/mapper/mpathX #For xfs
Apply a volume label to an existing filesystem:
# tune2fs -L appfs /dev/sdX #For ext4
# xfs_admin -L appfs /dev/mapper/mpathX #For xfs
Remove a volume label from an existing filesystem:
# tune2fs -L "" /dev/sdX #For ext4
# xfs_admin -L "--" /dev/mapper/mpathX #For xfs