
Troubleshooting and Problem Solving
DataDirect Networks EF2800 FC RAID Storage System User Guide (V 1.0)
161
10.10 Array Problems
Problem: Array is much smaller than it should be.
The backoff percent may be set higher than 1%, which is causing the
array to be much smaller than the full size of its member disks.
N
OTE
:
We strongly recommend that you leave the backoff percent at
1%.
Setting the backoff percent “backs off” or reduces the capacity of the
array by the given percentage. The backoff percentage helps when you
assign spares by compensating for the minor capacity differences that
occur between vendors. For example, two 18-GB drives from two
different vendors may differ in capacity by 100 MB. With a backoff of
0%, you would not be able to replace an array member’s slightly larger
18-GB drive with a smaller 18-GB drive. If you intend to only use
identical drives from the same vendor, you can use a backoff of 0%.
The default setting is 1% backoff. This default allows you to easily work
with drives that have the same nominal capacity, but different actual
capacities. The backoff percentage affects all arrays created on the
EF2800 after you set the percentage.
If the drives in an array are not equal in size, the array capacity in a
RAID 5 array is based on the smallest member’s capacity. The backoff
percentage is then taken off the capacity from that amount.
To change the backoff percentage via SAM:
1. From SAM, select Manage EF2800 > General Config > Option
Configuration. The Option Configuration page displays.
2. Enter the Backoff Percent you want. Enter the percentage as
three digits using the following format: 00.0%. The default setting
is 01.0%.
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