About site-based allocation


About site-based allocation
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Site-based allocation policies are enforced by default in a site-configured disk group. Site-based allocation requires that each volume has at least one plex at each site that is configured in the disk group. When a new volume is created in a site-configured disk group, the allsites attribute set to on, by default. The allsites attribute indicates that the volume must have at least one plex on each configured site in the disk group. For new volumes, the read policy is set to siteread by default.

If mirroring across sites is not required, or is not possible (as is the case for RAID-5 volumes), specify the allsites=off attribute to the vxassist command. If sites are configured in the disk group, a plex will always be confined to a site and will not span across sites. This enforcement cannot be overridden.

Before adding a new site to a disk group, be sure to meet the following requirements:

Disks from the site being added (site tagged) are present or added to the disk group.
Each existing volume with allsites set in the disk group must have at least one plex at the site being added. If this condition is not met, the command to add the site to the disk group fails. If the -f option is specified, the command does not fail, but instead it sets the allsites attribute for the volume to off.

Note:

By default, volumes created will be mirrored when sites are configured in a disk group. Initial synchronization occurs between mirrors. Depending on the size of the volume, synchronization may take a long time. If you do not need to perform an initial synchronization across mirrors, use init=active with the vxassist command.