Release Notes

Linux setup and configuration
26 Dell EMC PowerVault ME4 Series and Linux | 3924-BP-L
• Snapshot schedules can be created on individual volumes in ME Storage Manager. Currently, it is not
possible to create a schedule against a group of volumes. Therefore, it becomes a challenge to
coordinate taking consistent snapshots for multiple volumes. One option is to write a script that
incorporates the necessary steps to take a consistent snapshot. The following shows an example of
the high-level tasks to be included in the script.
a. Connect to the host.
b. Pause/stop the applications.
c. Connect to the ME4 Series system.
d. Identify the volumes to create snapshots.
e. Create snapshots on the volumes.
f. Connect to the host.
g. Resume/start the applications.
• Schedule the script to run periodically using an external scheduler such as Linux cron or other third-
party commercial schedulers.
3.4.2 Physical volume data alignment
It might be necessary to specify data alignment on LVM physical volumes (PV) to avoid data misalignment.
Since ME4 Series storage uses an internal chunk size ranging from 64k to 512k, it is recommended to
initialize LVM PV with a 1 MB alignment. Use pvcreate --dataalignment 1m to indicate the alignment starts
at 1 MB.
# pvcreate –-dataalignment 1m /dev/mapper/mpathb
3.4.3 Expand storage for LVM
Adding capacity to an existing LVM volume group can be performed in one of the two ways:
• Create new ME4 Series volumes and initialize them into the LVM volume group. It is recommended
that the new volumes are of equal capacity and have the same back-end storage type as the existing
volumes in the volume group. Once the volume group is expanded, the logical volume can be resized
to take up the new capacity. The advantage of this method is that existing volumes are not changed.
Only new volumes are introduced in the environment and can be backed out easily.
• Dynamically increase the size of existing ME4 Series volumes in ME Storage Manager. ME4 Series
storage can resize the virtual volumes without causing any application interruptions. On the Linux
host, resize the physical and multipath devices on the OS, then resize the logical volume and file
system. Depending on the file system type, the resize tasks can be done online without disrupting the
applications. Section 3.5.3 provides an example of this procedure. This method involves fewer
administrative tasks because there are no new volumes, new mappings, new snapshot schedules, or
new LVM physical devices to manage and set up.
3.5 File systems
ME4 Series storage supports a wide range of Linux file systems. This section focuses on two popular and
stable file systems: ext4 and xfs.