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3PAR disk relocation without offload of disk

 
yapkl
Trusted Contributor

Re: 3PAR disk relocation without offload of disk

If you're pushing to the max performance limits, then yes you should NOT mix the drive capacities in the same CPG. However, if you're not then it's not a big concern - personally I would mix all 10K into single CPG for easier management, considering that you will also be using AFC on SSD to help boost the random read performance.

Just imagine this, assume the drives are horses.

CPG_A : 16x1.2TB
CPG_B : 8x600G
CPG_C : 24x450G

BIG_CPG : 16x1.2TB + 8x600G + 24x450G = 48 spindles of 10K drives.

Now 3PAR architecture equally distributes the workloads. So if you have 3 separate CPGs, then only those disks in that CPG serves the I/O. Say you have a DB workload and you assign to CPG_B - the capacity & performance will only come from the 8x600G drives. That's not a lot of I/O potential, maybe 8x200 = 1600 IOPS. If you assign to BIG_CPG instead, you will get the capacity & performance from 24 spindles, or 3x more.

The issue with mixing drive capacities in same CPG is when the smaller drives are filled up, then the performance comes from the remaining disks, in situation above, it could be 450G filled up, then 600G and you'll end up with some volume performance coming from the 16x1.2TB or that these drives could be more heavily loaded that the other drives because it has to serve more capacity/IO. Then it might cause performance issues.

So as long as you're not pushing to the limits, AND you're using SSD (AFC or even AO - you will need license for that), then generally mixing capacities in same CPG makes it easier to manage the 3PAR.

There is no right or wrong, it really depends on the specific situation and your customer's storage admin preference.

 

Best Regards,

yapkl

Note: The opinions & comments above are my personal opinions, not of Hewlett Packard Enterprise
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