InfoScale™ 9.0 Solutions Guide - AIX

To convert a non-CDS disk group to a CDS disk group

1. If the disk group contains one or more disks that you do not want to convert to CDS disks, use the vxdg move or vxdg split command to move the disks out of the disk group.

2. The disk group to be converted must have the following characteristics:

   • No dissociated or disabled objects.

   • No sparse plexes.

   • No volumes requiring recovery.

   • No volumes with pending snapshot operations.

   • No objects in an error state.

   To verify whether a non-CDS disk group can be converted to a CDS disk group, type the following command:

   # vxcdsconvert -g diskgroup -A group

3. If the disk group does not have a CDS-compatible disk group alignment, the objects in the disk group must be relayed out with a CDS-compatible alignment.
4. If the conversion is not going to performed online (that is, while access to the disk group continues), stop any applications that are accessing the disks.
5. Type one of the following forms of the CDS conversion utility (vxcdsconvert) to convert a non-CDS disk group to a CDS disk group.

   # vxcdsconvert -g diskgroup [-A] [-d defaults_file] \
     [-o novolstop] alignment [attribute=value] ...
   # vxcdsconvert -g diskgroup [-A] [-d defaults_file] \
     [-o novolstop] group [attribute=value] ...

   The alignment and group keywords have the following effect:

   alignment	Specifies alignment conversion where disks are not converted, and an object relayout is performed on the disk group. A successful completion results in an 8K-aligned disk group. You might consider this option, rather than converting the entire disk group, if you want to reduce the amount of work to be done for a later full conversion to CDS disk group.
   group	Specifies group conversion of all non-CDS disks in the disk group before relaying out objects in the disk group.

   The conversion involves evacuating objects from the disk, reinitializing the disk, and relocating objects back to disk. You can specify the -o novolstop option to perform the conversion online (that is, while access to the disk group continues). If the -o novolstop option is not specified, stop any applications that are accessing the disks, and perform the conversion offline.

   Warning:

   Specifying the -o novolstop option can greatly increase the amount of time that is required to perform conversion.

   Conversion has the following side effects:

   • Non-CDS disk group are upgraded by using the vxdg upgrade command. If the disk group was originally created by the conversion of an LVM volume group (VG), rolling back to the original LVM VG is not possible. If you decide to go through with the conversion, the rollback records for the disk group will be removed, so that an accidental rollback to an LVM VG cannot be done.

   • Stopped, but startable volumes, are started for the duration of the conversion .

   • Any volumes or other objects in the disk group that were created with the layout=diskalign attribute specified can no longer be disk aligned.

   • Encapsulated disks may lose the ability to be unencapsulated.

   • Performance may be degraded because data may have migrated to different regions of a disk, or to different disks.

   In the following example, the disk group, mydg, and all its disks are converted to CDS while keeping its volumes still online:

   # vxcdsconvert -g mydg -o novolstop group \
     move_subdisks_ok=yes evac_subdisks_ok=yes \
     evac_disk_list=disk11,disk12,disk13,disk14

   The evac_disk_list attribute specifies a list of disks (disk11 through disk14) to which subdisks can be evacuated to disks by setting the evac_subdisks_ok option to yes.

   Before you use the vxcdsconvert command, make sure you understand its options, attributes, and keywords.

   See the vxcdsconvert(1M) manual page.