User`s guide

130 Implementing an Open IBM SAN
Selecting the storage type
To create RAID 5 volumes, we have to click on the RAID-5 Array row shown in
Figure 2-70.
Figure 2-70 Available Free Space frame, RAID-5 storage entry selected
If no storage type has been selected, the Volume Attributes field on the left hand
side shows only a volume size of zero.
Choosing the size and number of volumes
Once we have selected RAID-5 Array as the storage type, we can choose the
size and the number of the ESS logical volumes that we want to configure.
We are able to choose the size of the volumes granularity, beginning from 0.1 GB
up to the total capacity of our disk group, which is 210.45 GB, with a granularity
of 0.1 GB. We want to define four volumes with 16.1 GB each. The reason for the
volumes being exactly 16.1 GB, is that we want to all volumes the same size
without wasting any space. Defining volumes with a little less or a little more
space will mean that we will either fill the remaining space with smaller volumes
or waste space. For example, with a volume size of 16.2 GB, we could only
define 24 of them in two disk groups, which is shown in Figure 2-71.
Figure 2-71 Volume Attributes frame, ESS logical volume size of 16.2 GB selected
Note: An ESS logical volume can be as big as we want it to be within the
boundaries of one disk group. In our case, using 36.4 GB disks, we can have a
maximum volume size of 210.45 GB. Looking at the Information window on
the Storage Allocation — Graphical View panel we see 210.48 GB.