Silicon Graphics InfiniteStorage 4000 Series, Configuring And Maintaining, Page: 77 / 276

Chapter 4: Configuring a Storage Array 65
Hot spares are not required or needed for disk pools. Spare capacity for reconstruction
is divided among the drives within a disk pool. A small amount of each drive is
reserved as reconstruction space to hold reconstructed data in the event of loss of
access to a drive or a drive failure. Because of this behavior, the system can sustain
drive failures until the capacity is exhausted or the number of drives in the disk pool
falls below the minimum drive count. As long as free capacity exists on the system,
failed drives are rebuilt and degraded volumes are brought back to optimal. The only
constraint to rebuilding failed drives is the RAID level of the volumes in the disk pool.
In volume groups, the RAID level is determined when the volume group is created.
Each volume defined on the volume group inherits the same RAID level. The RAID
stripe width in a volume group is determined by the number of drives in the volume
group. Because of the way that the disk pool volume data is mapped onto the disk
pool, the stripe width is independent of the number of drives in the pool.
In your storage array, you want to configure as few disk pools as are required to
include every drive in the storage array as a member of one of the disk pools. Reasons
for having several disk pool in a storage array might include separate disk pools to use
certain types of drives, or to created different pools for different applications. For the
most efficient disk pool, all of the drives need to have the same characteristics:

Drive type (Fibre Channel or SAS)

Drive media (HDD or SSD)

Spindle speed

Security

Protection type

Capacity
Before you create a disk pool, run the
show storageArray
command to
determine the drives that are available and to make sure that you have enough drives
in the storage array to create a disk pool.
The
create diskPool
commands have several optional parameters to enable you
to create the configuration that you want. The use of these parameters is shown in the
examples in the following sections. For more information about the use of the
optional parameters refer to the
Command Line Interface and Script Commands
guide.
After you create the disk pool, you can create the volumes.
Creating Disk Pools
with
Software-Assigned
Drives
If you choose to let the storage management software assign the drives when you
create a disk pool, you need only to specify the type of drive that you want to use and
a name (user label) for the disk pool. Optionally, you also can specify the number of
drives that you want to use. The storage management software then assigns the drives.
The controller firmware assigns a number to the new disk pool. To create a disk pool
with software-assigned drives use this command: