LSI 1600 User Manual
Chapter 3 RAID Levels
19
RAID 3
RAID 3 provides disk striping and complete data redundancy though a dedicated parity drive. The
stripe size must be 64 KB if RAID 3 is used. RAID 3 handles data at the block level, not the byte
level, so it is ideal for networks that often handle very large files, such as graphic images.
stripe size must be 64 KB if RAID 3 is used. RAID 3 handles data at the block level, not the byte
level, so it is ideal for networks that often handle very large files, such as graphic images.
RAID 3 breaks up data into smaller blocks, calculates parity by performing an exclusive-or on the
blocks, and then writes the blocks to all but one drive in the array. The parity data created during
the exclusive-or is then written to the last drive in the array. The size of each block is determined
by the stripe size parameter, which is set during the creation of the RAID set.
blocks, and then writes the blocks to all but one drive in the array. The parity data created during
the exclusive-or is then written to the last drive in the array. The size of each block is determined
by the stripe size parameter, which is set during the creation of the RAID set.
If a single drive fails, a RAID 3 array continues to operate in degraded mode. If the failed drive is
a data drive, writes will continue as normal, except no data is written to the failed drive. Reads
reconstruct the data on the failed drive by performing an exclusive-or operation on the remaining
data in the stripe and the parity for that stripe. If the failed drive is a parity drive, writes will occur
as normal, except no parity is written. Reads retrieve data from the disks.
a data drive, writes will continue as normal, except no data is written to the failed drive. Reads
reconstruct the data on the failed drive by performing an exclusive-or operation on the remaining
data in the stripe and the parity for that stripe. If the failed drive is a parity drive, writes will occur
as normal, except no parity is written. Reads retrieve data from the disks.
Uses
Best suited for applications such as graphics, imaging,
video, or any application that calls for reading and writing
huge, sequential blocks of data.
video, or any application that calls for reading and writing
huge, sequential blocks of data.
Strong Points
Provides data redundancy and high data transfer rates.
Weak Points
The dedicated parity disk is a bottleneck with random I/O.
Drives
Three to 32
Cont’d