When you create the disk groups for a campus cluster, ensure that each disk group has the same number of disks on each physical site. You create each volume as a mirrored volume with one plex of the volume on Site A's storage array and the other plex of the volume on Site B's storage array.
Veritas recommends using the SFW site-aware allocation feature for campus cluster storage. Site-aware allocation can ensure that site boundary limits are maintained for operations like volume grow, subdisk move, and disk relocation.
Enabling site-aware allocation for campus clusters requires the following steps in the VEA:
After creating the disk groups, you tag the disks with site names to enable site-aware allocation. This is a separate operation, referred to in the VEA as adding disks to a site.
As an example, say you had a disk group with four disks. Disk1 and Disk2 are physically located on Site A. Disk3 and Disk4 are physically located on Site B. Therefore, you add Disk1 and Disk2 to "site_a" and add Disk3 and Disk4 to "site_b".
During volume creation, you specify the volume site type as Site Separated. This ensures that the volume is restricted to the disks on the selected site.
The hot relocation operation does not adhere to site boundary restrictions. If hot relocation causes the site boundary to be crossed, then the Site Separated property of the volumes is changed to Siteless. This is done so as not to disable hot relocation. To restore site boundaries later, you can relocate the data that crossed the site boundary back to a disk on the original site and then change back the properties of the affected volumes.
For more information on site-aware allocation, refer to the Storage Foundation Administrator's Guide.
When you create the volumes for a campus cluster, consider the following:
During disk selection, configure the volume as "Site Separated" and select the two sites of the campus cluster from the site list.
For volume attributes, select the "mirrored" and "mirrored across enclosures" options.
Veritas recommends using either simple mirrored (concatenated) or striped mirrored options for the new volumes. Striped mirrored gives you better performance compared to concatenated.
When selecting striped mirrored, select two columns in order to stripe one enclosure that is mirrored to the second enclosure.
During the volume creation procedure for Site Separated volumes, you can only create as many mirrors as there are sites. However, once volume creation is complete, you can add additional mirrors if desired.
Choosing "mirrored" and the "mirrored across" option without having two enclosures that meet requirements causes new volume creation to fail.
You cannot select RAID-5 for mirroring.
Selecting "stripe across enclosures" is not recommended because then you need four enclosures, instead of two.
Logging can slow performance.