HP StorageWorks HSG80 ACS Solution Software V8.8 for Sun Solaris Installation and Configuration Guide (AA-RV1RA-TE, March 2005)

Planning Storage Configurations
78 HSG80 ACS Solution Software V8.8 for Sun Solaris Installation and Configuration Guide
Figure 25: Three-member RAID 0 stripeset (example 2)
Keep the following points in mind as you plan your stripesets:
■ Reporting methods and size limitations prevent certain operating systems
from working with large stripesets.
■ A storageset should only contain disk drives of the same capacity. The
controller limits the effective capacity of each member to the capacity of the
smallest member in the storageset (base member size) when the storageset is
initialized. Thus, if you combine 9 GB disk drives with 4 GB disk drives in the
same storageset, you waste 5 GB of capacity on each 9 GB member.
If you need high performance and high availability, consider using a RAIDset,
striped-mirrorset, or a host-based shadow of a stripeset.
■ Striping does not protect against data loss. In fact, because the failure of one
member is equivalent to the failure of the entire stripeset, the likelihood of
losing data is higher for a stripeset than for a single disk drive.
For example, if the mean time between failures (MTBF) for a single disk is l
hour, then the MTBF for a stripeset that comprises N such disks is l/N hours.
As another example, if the MTBF of a a single disk is 150,000 hours (about
17 years), a stripeset comprising four of these disks would only have an
MTBF of slightly more than 4 years.
Virtual disk
Block 0
Block 1
Block 2
Block 3
Block 4
Block 5
etc.
Disk 1
Block 0
Block 3
etc.
Disk 2
Block 1
Block 4
etc.
Disk 3
Block 2
Block 5
etc.
Operating
system
view
Actual
device
mappings
Stripeset
CXO4592B