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Volume management
30 Dell EMC SC Series: Red Hat Enterprise Linux Best Practices | CML1031
Show volume labels and UUIDs on a filesystem using one of the following commands:
# blkid /dev/mapper/vgapp-lvapp
/dev/mapper/vgapp-lvapp: LABEL="appfs2" UUID="b060087c-fba6-4517-a386-
24dee0844f55" TYPE="xfs"
# lsblk -o name,mountpoint,label,size,uuid /dev/mapper/vgapp-lvapp
NAME MOUNTPOINT LABEL SIZE UUID
vgapp-lvapp /testfs appfs2 5G b060087c-fba6-4517-a386-24dee0844f55
# xfs_admin -lu /dev/mapper/vgapp-lvapp #For xfs
label = "appfs2"
UUID = b060087c-fba6-4517-a386-24dee0844f55
3.9.2 Persistent naming in /etc/fstab
The LABEL= or UUID= syntax can be used to reference volumes in a variety of places including mount
commands and entries in the /etc/fstab file. This provides the liberty of uniquely identifying the volumes
regardless of their discovery device name designations, multipath configurations, or predefined multipath
aliases.
Reference a filesystem using UUID or label in /etc/fstab:
UUID="b060087c-fba6-4517-a386-24dee0844f55" /testfs xfs defaults,discard 0 0
LABEL=appfs /testfs xfs defaults,discard 0 0
3.9.3 Filesystem space reclamation and SCSI UNMAP
For filesystem types that support the online SCSI TRIM/UNMAP command, such as ext4 and xfs, enable the
discard mount option in /etc/fstab or include –o discard to the manual mount command. For example,
mount -o discard /dev/mapper/vgapp-lvapp /testfs.
This allows space to be released back to the storage pool in the SC Series system when deleting files in the
filesystem. Administrators should review the filesystem documentation to confirm the availability of the
features.
As new data is written to the filesystem, actual space is consumed in SC Series storage. When files are
deleted from the filesystem, the operating system informs the SC Series storage system which data blocks
can be released. The release of storage is automatic and requires no additional steps. To confirm the release
of space in SC Series storage, monitor the Disk Usage on the LUN Summary page in the DSM GUI.
3.9.4 Filesystem mount options
When mounting a filesystem, consider the following options and guidelines:
• Identify the file system by its UUID, label, or LVM LV device in the /etc/fstab file. Avoid using any
non-persistent device paths such as /dev/sdX.
• Include discard in the mount option to enable space reclamation support for the filesystem.
• Include nofail in the mount option if the Linux operating system experiences mount issue during
system boot. This prevents interruption during the boot process which requires manual intervention.