Online Spares; Logical Storage Elements - HP ML110 G1 User Manual

the following table may help determine which option is best for different
situations.
Table 5 Summary of RAID methods
Maximum
number of hard
drives
Tolerant of
single hard
drive failure?
Tolerant of
multiple
simultaneous
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 will still fail.
NOTE:
based on the type of SAN the storage server is connected to. See the
individual SAN documentation for limitations of Windows Storage
Server 2003.

Logical storage elements

Logical storage elements consist of those components that translate the
physical storage elements to file system elements. The storage server
utilizes the WebUI to manage the various types of disks presented to the
RAID 0
Striping (no
fault tolerance)
N/A
No
No
For enterprise class storage servers, storage limitations are
RAID 1+0 RAID 5
Mirroring Distributed
Data
Guarding
N/A 14
Yes Yes
For RAID No
1+0, if the
failed drives
are not
mirrored to
each other
RAID ADG
Advanced Data
Guarding
Storage system
dependent
Yes
(two drives can
fail)
Storage Server user guide 27