HP StoreEasy 1000 Administrator's Manual page 95

Array configuration best practices
When you build an array:
All drives grouped in a logical drive must be of the same type. For example, all SAS or all
SATA and all hard drives or all solid state drives.
For the most efficient use of drive space, all drives within an array must have approximately
the same capacity. Each configuration utility treats each physical drive in an array as if the
drive has the same capacity as the smallest drive in the array. Any excess capacity of a
particular drive cannot be used in the array and is unavailable for data storage.
Increasing the number of drives configured in an array might result in a drive failure in the
array during the given period.
To guard against the data loss during a drive failure, configure all logical drives in an array
with a suitable fault-tolerance (RAID) method.
A rebuild operation requires approximately 15 to 30 seconds per gigabyte for RAID 5 or RAID
6. Actual rebuild time depends on several factors, such as the amount of I/O activity that occurs
during the rebuild operation, the number of disk drives in the logical drive, the rebuild priority
setting, and the disk drive performance. You can view the rebuild progress and set the priority
for the rebuild operation by using ACU or SSA.
Typically, using larger LUNs, which require larger pools simplifies storage management and
namespace management, especially when using storage for file shares. However, the following
factors can affect the use of larger LUNs:
Backup strategy
◦
Larger LUNs require longer backup windows.
◦
Multiple, smaller LUNs may be more efficient for backup and recovery scenarios.
Performance requirements
◦
If there are performance requirements for specific clients, segmenting groups of clients
onto different LUNs might be useful.
Drive availability
◦
Starting with a full disk enclosure provides the most options for creating pools. A disk
enclosure with a smaller number of drives has a smaller number of pooling options.
◦
RAID migration is not allowed. For example, you start with a pool containing 13 drives
that are configured with RAID 5 and then create a LUN (virtual disk) that fills the pool.
Later, you decide to grow that LUN. Although a 22-drive pool set may be listed, you
cannot grow a 13-drive pool into a 22-drive pool because the 22-drive pool requires
RAID 50 or RAID 60. Migrating from RAID 5 to RAID 50 or RAID 60 is not supported.
Using Pool Manager 95