Managing IBM Storage Scale RAID with the mmvdisk command

The mmvdisk command is an integrated command suite and management methodology for IBM Storage Scale RAID. It provides a unified conceptual framework that simplifies many of the more complicated aspects of IBM Storage Scale RAID administration.

The mmvdisk command enforces and encourages IBM Storage Scale RAID best practices with respect to the following tasks:

  • IBM Storage Scale RAID server configuration by using the mmvdisk server sub-command.
  • Recovery group creation and management by using the mmvdisk recoverygroup sub-command.
  • The definition, sizing, and creation of vdisk NSDs by using the mmvdisk vdiskset sub-command.
  • The creation of vdisk-based file systems by using the mmvdisk filesystem sub-command.

Compatibility between mmvdisk and the legacy IBM Storage Scale RAID command set is strictly limited. For example, a recovery group that has been created using mmvdisk cannot be deleted using mmdelrecoverygroup.

The mmvdisk command can manage all three types of IBM Storage Scale RAID recovery groups:
  1. The paired recovery groups of Elastic Storage Server, where a pair of servers divide a common set of disk enclosures into a pair of recovery groups, with each server taking exclusive primary responsibility for one recovery group of the pair.
  2. The scale-out recovery groups of IBM Spectrum® Scale Erasure Code Edition, where a set of 4 to 32 identically equipped servers each take an equal share of responsibility in a single collective recovery group.
  3. The shared recovery groups of IBM Elastic Storage® System 3000, where a single recovery group is defined on a common disk enclosure shared by two servers.

A recovery group that is managed by the mmvdisk command is called an mmvdisk recovery group. It cannot be managed using the legacy IBM Storage Scale RAID command set.

A recovery group that is managed using the legacy IBM Storage Scale RAID command set is called either a non-mmvdisk recovery group or a legacy recovery group. It cannot be managed using mmvdisk other than to be converted from legacy management to mmvdisk management.

A new IBM Storage Scale cluster can use mmvdisk from the beginning to manage any IBM Storage Scale RAID recovery groups. The server and recovery group pairs of existing Elastic Storage Server installations can be converted to enable mmvdisk management. All existing non-mmvdisk recovery groups in a cluster must be converted to mmvdisk management before mmvdisk can be used to create new recovery groups in the cluster.

The scale-out recovery groups of IBM Storage Scale Erasure Code Edition and the shared recovery groups of IBM Elastic Storage System 3000 must be managed by mmvdisk. If a cluster containing non-mmvdisk paired recovery groups wishes to add scale-out or shared recovery groups, the existing paired recovery groups must first be converted to mmvdisk management.

When all recovery groups in an IBM Storage Scale cluster are managed by mmvdisk, the legacy IBM Storage Scale RAID commands will refuse to create new recovery groups. All further IBM Storage Scale RAID administration must be performed using mmvdisk.

For the management of IBM Storage Scale file system vdisk NSDs in recovery groups, the central concept in mmvdisk is that of a vdisk set. A vdisk set is a collection of uniform vdisk NSDs from one or more recovery groups. The member vdisk NSDs of a vdisk set all have the same attributes in each of the vdisk set's recovery groups. Vdisk sets provide a scalable specification template, which are applicable across multiple recovery groups for sizing and creating uniform vdisk NSDs. The vdisk NSDs of a vdisk set are then managed as a unit.

A vdisk-based file system is constructed from one or more vdisk sets. Each vdisk set in a file system contributes all of its member vdisk NSDs to the file system. A vdisk set must belong in its entirety to exactly one file system, but multiple entire vdisk sets can be combined to construct a single vdisk-based file system.