10-19-2009 08:06 AM
can you mix the boxes of 8 and 12 disk in the same cluster,
can you mix different disk size boxes in the same cluster??
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10-19-2009 08:21 AM
You technically CAN mix 8 and 12 disk units together, however you will only get the IOP performance as if you were running all 8 disk units. A cluster will always drop to the lowest common denominator.
Same rule from above applies with size: If you have a cluster that contains:
1 unit of 8x146GB (RAID 5)
1 unit of 8x300GB (RAID 5)
= 1022 x 2 = 2044GB.
Any larger nodes will actually display "some stranded space" indicating such.
10-29-2009 11:56 AM
When it comes to performance though everything does not just drop to the lowest common denominator. Everything, on average, ends up somewhere in the middle actually. And you'll get inconsistent results in that which node you happened to get load balanced to will have some affect on what you actually see.
This means that clusters of dissimilar nodes yields somewhat unpredictable performance results.
The capacity utilization on the other hand is totally predictable.
SAN/iQ (P4000 SANs) allow you to mix clusters in any way you want. RAID types, nodes, size, disk type, anything. As long as they are running the same, or even close to the same, version SAN/iQ you can mix them. Mostly this is to allow for all the different combiniations of possible migration scenarios and there are some node types that make complete sense to mix.
One of the most common mixes are nodes that might be slightly different hardware, but still ran the same disk # and architecture. For example, mixing the DL320s nodes, the NSM 2120, the NSM 2120 G2, and the P4500 makes complete sense and is expected. They were/are all 12 drive nodes, just different generations.
10-29-2009 12:40 PM
Performance will be unpredictiblem, and CAN be as low as the poorest performing node in your cluster.. Depending on load balancing, gateway etc etc.