HP Array Controller HSG V8.7 Software - Manual (Page 91)

Creating Storagesets 3–13
n You can configure up to 30 mirrorsets per controller or pair of dual-
redundant controllers. Each mirrorset contains a minimum of one
and a maximum of six members.
n A write-back cache module is required for mirrorsets, but write-
back cache need not be enabled for the mirrorset to function
properly.
n Both write-back cache modules must be the same size.
n If you’re using more than one mirrorset in your subsystem, you
should put the first member of each mirrorset on different buses as
shown in Figure 3–6. (The first member of a mirrorset is the first
disk drive you add.)
When a controller receives a request to read data from a mirrorset, it
typically accesses the first member of the mirrorset. Read access
depends upon the read source switches, as described in “Read
Source,” page 3–43. If you have several mirrorsets in your
subsystem and their first members are on the same bus, that bus will
be forced to handle the majority of traffic to your mirrorsets. When
a controller receives a request to write data to a mirrorset, it
accesses and writes to all members.
Figure 3–6 First Mirrorset Members on Different Buses
To avoid an I/O bottleneck on one bus, you can simply put the first
members on different buses. Additionally, you can set the read-
source switch to Round Robin. See “Read Source,” page 3–43, for
more information about this switch.
n Place mirrorsets and RAIDsets on different ports to minimize risk
in the event of a single port bus failure.
CXO5506A
First member
of Mirrorset 1
First member
of Mirrorset 2