HP StorageWorks 2000 Series Reference Manual page 253

50 6
6 4
Non- 1
RAID
A virtual disk can contain different models of disk drives, even disk drives with
different capacities. For example, a virtual disk can include a 250-Gbyte disk drive
and a 500-Gbyte disk drive. If you mix disk drives with different capacities, the
smallest disk drive determines the logical capacity of all other disk drives in the
virtual disk, regardless of RAID level. For example, if a RAID 0 virtual disk
contains one 250-Gbyte disk drive and four 500-Gbyte disk drives, the capacity of
the virtual disk is equivalent to approximately five 250-Gbyte disk drives. To
maximize capacity, use disk drives of similar size.
For greatest reliability, use disk drives of the same size and rotational speed.
Combination of RAID 0
(data striping) and RAID
5 with distributed parity
Block-level data striping
with distributed parity
Non-RAID, nonstriped
mapping to a single disk
drive
Better random read and
write performance and
data protection than
RAID 5; supports more
drives than RAID 5
Best suited for large
sequential workloads;
non-sequential read and
sequential read/write
performance is
comparable to RAID 5
Ability to use a single
disk drive to store
additional data
Lower storage capacity
than RAID 5
Higher redundancy cost
than RAID 5 because the
parity overhead is twice
that of RAID 5; not
well-suited for
transaction-oriented
network applications;
non-sequential write
performance is slower
than RAID 5
Not protected, lower
performance (not
striped)