Online Spares; Summary Of Raid Methods - HP ML110 G1 User Manual

the following table can help determine which option is best for different
situations.
Table 6 Summary of RAID Methods
Maximum
number of
hard drives
Tolerant
of single
hard drive
failure?
Tolerant of
multiple si-
multaneous
hard drive
failure?

Online Spares

Further protection against data loss can be achieved by assigning an
online spare (or hot spare) to any configuration except RAID 0. This hard
drive contains no data and is contained within the same storage sub
system as the other drives in the array. When a hard drive in the array
fails, the controller can then automatically rebuild information that was
originally on the failed drive onto the online spare. This quickly restores the
system to full RAID level fault tolerance protection. However, unless RAID
ADG is being used, which can support two drive failures in an array, in the
unlikely event that a third drive in the array should fail while data is being
rewritten to the spare, the logical drive still fails.
NOTE:
For configurable storage servers, storage limitations are based on the
type of SAN the storage server is connected to. See the individual SAN
documentation for limitations of Windows Storage Server 2003.
RAID 0 RAID 1+0
Striping Mirroring
(no fault
tolerance)
N/A N/A
No Yes
No For RAID
1+0, if
the failed
drives
are not
mirrored to
each other
HP ProLiant Storage Server user guide
RAID 5
RAID ADG
Distributed
Advanced
Data
Guarding Guarding
14 Storage
system
dependent
Yes Yes
No Yes (two
drives can
fail)
Data
35