Storage Area Networks For Dummies®

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Par t II: Designing and Building a SAN
The configuration of your pretend SAN has two hosts: a Unix server and a
Windows server. Each has an application needing one LUN or disk. Although
you could put hundreds of LUNs out to these servers in the same way, I’m
keeping things simple for this chapter.
RAID setup
The Unix server requires a LUN that comes from a RAID 10 array. Because
of the application’s need for very fast and random write input/output (I/O),
RAID 10 fits the bill. The Windows server, on the other hand, does simple file
sharing, that is, lots of reads and not much write activity. Put that LUN on a
RAID 5 set; doing so wastes less space on reliability. (RAID 10 uses 50 percent
of the physical space for its data protection; RAID 5 loses only the space of
one physical disk in the set.) Figure 7-7 shows the proposed disk layout for
Larry-the-storage-array.
Storage array: Larry
Figure 7-7:
Array configuration:
How to
carve up the
pretend disk
drives.
1 2 3 7 8 9
RAID 10
RAID 5
RAID Group #1
RAID Group #2
4
LUN #1
LUN #2
5 6
10
Spare disk
A1 A2 B1 B2
Controller A
Controller B
Carving up the storage array
Now create some RAID sets. Make two RAID sets, like those in Figure 7-7 —
one RAID 10 with six disks (three data and three mirrors) and one RAID 5
set of three disks (two data and one parity drive). Use the addraidgroup
parameter to accomplish this as an additional parameter to arraycfg. It
looks like this: