IBM System Storage DS3000, Programming Manual

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Table 4-8. Drive Counts and the Number of Disk Drives Reserved for Reconstruction (continued)
Drive
Count Drives Reserved for
Reconstruction
Comments
32 - 63 3
64 - 123 4
128 -
191 6
192-255 7 The maximum configuration of DS3500 and DCS3700 is 192 drives
256 -
360 8 The maximum configuration of DCS3700 storage system with Performance Module
Controllers is 360 drives
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 logical drives are brought back to optimal. The only constraint to rebuilding failed
drives is the RAID level of the logical drives in the disk pool.
In your storage subsystem with controller firmware version 7.83.xx.xx and later, you can create upto 10
disk pools. Reasons for having several disk pools in a storage subsystem might include separate disk
pools to use certain types of drives, or to create different pools for different applications. For the most
efficient disk pool, all of the drives need to have the same characteristics:
v
Drive type (SAS)
v Drive media (HDD)
v
Spindle speed
v
Full-Disk Encryption (FDE)
v
T10PI
v
Capacity
Before you create a disk pool, run the
show storageSubsystem
command to determine the drives that are
available, and to make sure that you have enough drives in the storage subsystem to create a disk pool.
The
create diskPool
command has several optional parameters to enable you 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 Chapter 3 of this guide.
In a disk pool, you must create the disk pool first and then the logical drives.
Creating disk pools with software-assigned disk drive
If you choose to let the storage management software assign the disk drive when you create a disk pool,
you need only to specify the type of disk drive that you want to use and a name (
user label
) for the
disk pool. Optionally, you can also specify the number of disk drives that you want to use. The storage
management software then assigns the disk drive. The controller firmware assigns a number to the new
disk pool. To create a disk pool with a software-assigned disk drive, use this command:
create diskPool diskDriveType=(fibre|sas)
userLabel="diskPoolName"
[diskDriveCount=diskDriveCountValue |
warningThreshold=(warningThresholdValue|default) |
criticalThreshold=(criticalThresholdValue|default) |
criticalPriority=(highest|high|medium|low|lowest) |
backgroundPriority=(highest|high|medium|low|lowest) |
Chapter 4. Configuring a Storage Subsystem
4-39