Dell POWERVAULT MD3600I - Manual (Page 97)

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Disk Pools And Disk Pool Virtual Disks
Disk pooling allows you to distribute data from each virtual disk randomly across a set of physical disks. Disk pooling
provides RAID protection and consistent performance across a set of physical disks logically grouped together in the
storage array. Although there is no limit on the maximum number of physical disks that can comprise a disk pool, each
disk pool must have a minimum of 11 physical disks. Additionally, the disk pool cannot contain more physical disks than
the maximum limit for each storage array. The physical disks in each disk pool must:
• be SAS or nearline SAS
• have the same physical disk speed (RPM)
NOTE: The maximum physical disk speed is 15,000 rpm for standard SAS and 7,500 rpm for 3.5" nearline
SAS.
NOTE: In a disk pool, the physical disks must have the same capacities. If the physical disks have different
capacities, the MD Storage Manager uses the smallest capacity among the physical disks in the pool. For
example, if your disk pool is comprised of several 4 GB physical disks and several 8 GB physical disks, only
4 GB on each physical disk is utilized.
The data and redundancy information in a disk pool is distributed across all of the physical disks in the pool and provides
the following benefits:
• Simplified configuration
• Better utilization of physical disks
• Reduced maintenance
• the ability to use thin provisioning
Difference Between Disk Groups And Disk Pools
Similar to a disk group, you can create one or more virtual disks in a disk pool. However, the disk pool differs from a disk
group in the way data is distributed across the physical disks comprising the pool.
In a disk group, data is distributed across the physical disks based on RAID level. You can specify a RAID level when you
create the disk group, then the data for each virtual disk is written sequentially across the set of physical disks
comprising the disk group.
NOTE: Because disk pools can co-exist with disk groups, a storage array can contain both disk pools and disk
groups.
Disk Pool Restrictions
CAUTION: If you downgrade the RAID controller module firmware version of a storage array that is configured with
a disk pool to a firmware version that does not support disk pools, the virtual disks are lost and the physical disks
are treated as unaffiliated with a disk pool.
• All physical disk media types in a disk pool must be the same. Solid State Disks (SSDs) are not supported.
• You cannot change the segment size of the virtual disks in a disk pool.
• You cannot export a disk pool from a storage array or import the disk pool to a different storage array.
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