Outline of an mmvdisk use case

The mmvdisk command assumes that the IBM Spectrum Scale™ cluster is installed and configured properly with respect to licenses, quorum and node designations, and network connectivity.

The intended IBM Spectrum Scale RAID recovery group server nodes should be properly connected to the disks that will make up the recovery groups. The mmvdisk command can be used to validate that these servers detect a supported disk topology.

The basic use case for creating vdisk-based file systems with mmvdisk follows this sequence of steps:

Creating recovery group server node classes. For ESS recovery group pairs, mmvdisk is used to create an mmvdisk node class for each ESS server pair. Each node class contains exactly one ESS server pair.
```
# mmvdisk nodeclass create --node-class ESS01 -N server01,server02
```
Verifying recovery group server disk topologies. Next, mmvdisk is used to verify that the intended supported server disk topology is detected on the node class.
```
# mmvdisk server list --node-class ESS01 --disk-topology
```
Configuring recovery group servers. Next, mmvdisk is used to configure each node class as GNR recovery group servers. Each server node class is configured independently of other nodes or node classes.
```
# mmvdisk server configure --node-class ESS01 --recycle all
```
Creating recovery groups. Once an mmvdisk node class is configured and verified to have the correct disk topology, mmvdisk is used to create the two ESS recovery groups for the node class.
```
# mmvdisk recoverygroup create --recovery-group ESS01L,ESS01R --node-class ESS01
```
Defining vdisk sets. Once the recovery groups are created, mmvdisk is used to define vdisk sets in the recovery groups. The vdisk set definitions are specification templates that are sized within one or more recovery groups, which allows the disk space and server memory demands to be previewed and evaluated before any vdisk NSDs are actually created.
```
# mmvdisk vdiskset define --vdisk-set vs1 --recovery-group ESS01L,ESS01R --code 8+3p --block-size 4m --set-size 50%
# mmvdisk vdiskset define --vdisk-set vs2 --recovery-group ESS01L,ESS01R --code 4+2p --block-size 512k --set-size 25%
```
As long as the actual vdisk NSDs have not been created, vdisk sets can be undefined and defined again until the attributes and disk and memory sizes are satisfactory.
Creating vdisk NSDs. When the vdisk set definitions have been satisfactorily sized, mmvdisk is used to create the actual vdisk NSDs in the recovery groups.
```
# mmvdisk vdiskset create --vdisk-set vs1,vs2
```
Creating vdisk-based file systems. Once vdisk sets are created, mmvdisk is used to create file systems that use the vdisk NSDs from one or more vdisk sets.
```
# mmvdisk filesystem create --file-system fs1 --vdisk-set vs1
# mmvdisk filesystem create --file-system fs2 --vdisk-set vs2
```