Dell PowerVault DP600 - Manual (Page 10)

10
Expanding Disk Storage
NOTE:
A maximum of eight physical disks within each RAID 5 disk group is
recommended.
NOTE:
All disk drives added to a disk group should be the same size. When
combining drives of dissimilar size for RAID 5, the size of the smallest drive will be
used by each disk within that disk group. As a result, using a larger drive wastes its
disk space.
NOTE:
It is not required to have the same size of disks in each of your RAID disk
groups. For example, if your internal RAID disk group is made up of four 250GB
drives, you could add an external RAID group made up of five 500GB disk drives.
Figure 2-2. Dissimilar Disks in a RAID Group
Benefits of Hot Spares
For additional protection against a single disk failure, add a global hot spare to
your RAID configuration. The physical disk assigned as a hot spare
automatically replaces the physical disk on which an error has been detected.
The caveat to using a hot spare is that you lose a storage slot within the
system or external storage enclosure that could have been used by a data disk.
RAID 5 configurations protect against "single" disk failures. A hot spare
provides unattended and uninterrupted protection against an additional disk
failure.
There are two types of hot spares that can be allocated: global or dedicated. If
you choose to implement a hot spare, global hot spares are recommended.
Refer to the "Assign and Unassign Global Hot Spare" section of your Dell
OpenManage Server Administrator User's Guide for more information on how
to configure global hot spares.
250GB 250GB 500GB 500GB
wasted space
in RAID group