AMCC 9000 User Manual

Page of 126
Understanding RAID Concepts and Levels
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disk arrays achieve highest transfer rates and performance at 
the expense of fault tolerance. 
„
Distributed Parity
. Parity works in combination with striping 
on RAID 5 and RAID 50. Parity information is written to each 
of the striped drives, in rotation. Should a failure occur, the data 
on the failed drive can be reconstructed from the data on the 
other drives. 
„
Hot Spare
. A single drive that is not used for user data, but 
rather as an extra drive that is online and available to 
automatically take the place of any drive that fails in a 
redundant unit. Used with RAID 1, 5, 10 and 50. 
„
Hot Swap
. The process of exchanging a drive without having 
to shut down the system. This is useful when you need to 
exchange a degraded drive. It is also useful if you want to add 
disk drives to configure into a unit without shutting down the 
system first.
Configurations Available with the 3ware RAID Controller
The following RAID levels and configurations are available for 
drives attached to a 3ware RAID controller: 
„
RAID 0
. Provides striping, but no mirroring or redundancy of 
any kind. Striped disk arrays achieve high transfer rates 
because they can read and write data on more than one drive 
simultaneously. The stripe size is configurable in 3ware BIOS 
Manager (3BM). Requires a minimum of two drives. 
When drives are configured in a striped disk array, large files 
are distributed across the multiple disks using RAID 0 
techniques. 
Striped disk arrays give exceptional performance, particularly 
for data intensive applications such as video editing, computer-
aided design and geographical information systems. 
RAID 0 arrays are not fault tolerant; the loss of any drive 
results in the loss of all the data in that array, and can even