Compaq StorageWorks HSG60 ACS Solution Software V8.6 for Compaq Tru64 UNIX Installation and Configuration Guide

2–12 HSG60 ACS Solution Software Version 8.6 for Compaq Tru64 UNIX Installation and Configuration Guide
Figure 2–8. A 3-member RAID 0 stripeset (example 2)
Keep the following points in mind when planning 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 will
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