Specifications

SCSI to SATA RAID Subsystem | Administrator’s Manual Array Expansion | en 161
Bosch Security Systems F.01U.027.802 | V1 | 2006.11
11 Array Expansion
The array expansion functions allow you to expand storage capacity without the cost of buying
new equipment. Expansion can be completed on-line while the system is serving host I/Os.
11.1 Overview
What is RAID Expansion and how does it work?
Before the invention of RAID Expansion, increasing the capacity of a RAID system meant back-
ing up all data in the disk array, re-creating the disk array configuration with new drives, and
then restoring data back into system.
RAID Expansion technology allows users to expand a logical drive by adding new drives, or
replacing drive members with drives of larger capacity. Replacing is done by copying data
from the original members onto larger drives; the smaller drives can then be replaced without
powering down the system.
11.2 Notes on Expansion
11.2.1 Added Capacity
When a new drive is added to an existing logical drive, the capacity brought by the new drive
appears as a new partition. For example, if you have 4 physical drives (36GB each) in a logical
drive, and each drive’s maximum capacity is used, the capacity of the logical drive will be
108GB. (One drive’s capacity is used for parity, e.g., RAID 3). When a new 36GB drive is
added, the capacity will be increased to 144GB in two separate partitions (one is 108GB and
the other 36GB).
11.2.2 Size of the New Drive
A drive used for adding capacity should have the same or more capacity as other drives in the
array.
11.2.3 Applicable Arrays
Expansion can only be performed on RAID 0, 1, 3 and 5 logical drives. Expansion cannot be
performed on logical configurations that do not have parity, e.g., NRAID or RAID 1.
i
NOTICE!
Expansion on RAID0 is not recommended, because the RAID0 array has no redundancy. Inter-
ruptions during the expansion process may cause unrecoverable data loss.