Basic disk pools and independent disk pools, also called auxiliary storage
pools (ASPs) in the character-based interface, are both useful to group disk
units containing certain information together; however, they have some inherent
differences:
- When the server performs an IPL, all of the disk units configured to a
basic disk pool must be accounted for in order for the server to continue
the IPL. Independent disk pools are not included in the IPL. When you vary
on the independent disk pool, the node then verifies that all disk units are
present.
- When an unprotected disk unit in a disk pool fails, it typically stops
all normal processing on the server until it can be repaired. The total loss
of a disk unit in a basic disk pool requires lengthy recovery procedures to
restore the lost data before the server can IPL and resume normal operations.
- The data in a basic disk pool belongs to the attaching node and can only
be directly accessed by that system. In an independent disk pool the data
does not belong to the node, but it belongs to the independent disk pool.
You can share the data in the independent disk pool between nodes in a cluster
by varying it off of one node and varying it on to another node.
- When you create a basic disk pool, you assign the disk pool a number.
When you create an independent disk pool, you name the disk pool and the system
assigns a number.
- If a basic disk pool fills up, it can overflow excess data into the system
disk pool. When this occurs, the disk pool loses the isolation and protection
inherent in disk pools. Independent disk pools cannot overflow. If they did,
they lose their independence. When the independent disk pool nears its threshold,
you need to add more disk units or delete objects to create more storage space.
- When you make restricted changes to disk configuration in a basic disk
pool you must have your server restarted to Dedicated Service Tools (DST).
In an offline independent disk pool you do not need to have your server in
DST mode to start or stop mirroring, start device parity protection, start
compression, remove a disk unit, and so on.