Managing IBM Spectrum Scale RAID with the mmvdisk command

The mmvdisk command provides a unified conceptual framework that simplifies many of the more complicated aspects of IBM Spectrum Scale™ RAID administration.

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

• IBM Spectrum Scale RAID server configuration (mmvdisk server)
• Recovery group creation (mmvdisk recoverygroup)
• The definition, sizing, and creation of vdisk NSDs (mmvdisk vdiskset)
• The creation of vdisk-based file systems (mmvdisk filesystem)

The mmvdisk command does this without the manual stanza file editing required by many of the legacy IBM Spectrum Scale RAID commands.

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 is applicable across multiple recovery groups, for sizing and creating uniform vdisk NSDs. The vdisk NSDs 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 a file system can be constructed from multiple vdisk sets.

Compatibility between mmvdisk and the legacy IBM Spectrum Scale RAID commands is strictly limited.

The mmvdisk command provides a command for converting legacy IBM Spectrum Scale RAID recovery groups, servers, vdisks, and file systems to mmvdisk management.

Until a recovery group is converted to mmvdisk management, only the legacy IBM Spectrum Scale RAID commands can be used to manage the recovery group and its servers and vdisks; mmvdisk recognizes the recovery group as non-mmvdisk and refuses to manage it.

Until all existing legacy recovery groups are converted to mmvdisk management, mmvdisk refuses to create new recovery groups.

The legacy IBM Spectrum Scale RAID commands also refuse to manage a recovery group that is created by or converted to mmvdisk management.

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