HP Integrity NonStop J-Series User Manual
Page 53
Configuring and Managing SMF Processes
HP NonStop Storage Management Foundation User's Guide—523562-007
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Considerations for Pooling
Longer recovery time for a physical disk failure
More overhead when updating disk statistics and in the VDP’s placement
decisions, because every VDP must register the location of every disk in the pool
Larger impact if the pool process fails
Another approach might be to use one pool per disk. But, again, this method has
disadvantages:
The benefits of placement and relocation are lost
Big disk configuration require many more pool processes
Because pools grow one or more disks at a time, pool size would have to be
doubled to increase its capacity
Alternate methods for configuring your pools will provide better solutions than a single
large pool or a disk per pool. Each pool can require a different method. It is critical to
understand the design and performance characteristics of the current or planned
application when deciding which method to use. Some methods to consider are:
One pool per CPU:
Provides performance gain from co-locating the DP2 processes, the pool
process, and the VDPs in the same CPU
Limits impact of a CPU outage to a single pool
Provides natural and easy to remember way to subdivide a large disk operation
Pooling across multiple CPUs:
Provides greater parallelism
Allows relocation to balance CPU load
Is a good strategy when the disk per CPU ratio is low
Pooling by disk attribute (for example, mirror and audited):
Simplifies placement of files with special requirements
Pooling for disk space considerations:
Provides that any VDP can use up all the free space in its pool
Limits the impact any one VDP can have on overall free space
Provides that the disk full threshold is set at the pool level
Pooling by group or application:
Provides that a group or application “owns” the pool
Limits impact of physical disk outage
Simplifies space growth planning