Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 04-08-2006 Installation Manual page 133

parity disk and cannot service simultaneous multiple requests. Both levels are only
rarely used.
RAID 4
Level 4 provides block-level striping just like Level 0 combined with a dedicated
parity disk. In the case of a data disk failure, the parity data is used to create a re-
placement disk. However, the parity disk may create a bottleneck for write access.
Nevertheless, Level 4 is sometimes used.
RAID 5
RAID 5 is an optimized compromise between Level 0 and Level 1 in terms of
performance and redundancy. The hard disk space equals the number of disks used
minus one. The data is distributed over the hard disks as with RAID 0. Parity blocks,
created on one of the partitions, are there for security reasons. They are linked to
each other with XOR, enabling the contents to be reconstructed by the corresponding
parity block in case of system failure. With RAID 5, no more than one hard disk
can fail at the same time. If one hard disk fails, it must be replaced as soon as pos-
sible to avoid the risk of losing data.
Other RAID Levels
Several other RAID levels have been developed (RAIDn, RAID 10, RAID 0+1,
RAID 30, RAID 50, etc.), some of them being proprietary implementations created
by hardware vendors. These levels are not very widespread, so are not explained
here.
6.2.2 Soft RAID Configuration with YaST
The YaST soft RAID configuration can be reached from the YaST Expert Partitioner,
described in Section 7.5.8, "Partitioner"
to edit and delete existing partitions and create new ones that should be used with soft
RAID. There, create RAID partitions by first clicking Create → Do not format then
selecting 0xFD Linux RAID as the partition identifier. For RAID 0 and RAID 1, at least
two partitions are needed—for RAID 1, usually exactly two and no more. If RAID 5
is used, at least three partitions are required. It is recommended to take only partitions
of the same size. The RAID partitions should be stored on different hard disks to decrease
the risk of losing data if one is defective (RAID 1 and 5) and to optimize the performance
of RAID 0. After creating all the partitions to use with RAID, click RAID → Create
RAID to start the RAID configuration.
(page 161). This partitioning tool enables you
Advanced Disk Setup 133