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EVA5000 and Performance

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Hermanator
Occasional Contributor

EVA5000 and Performance

Is there a performance gain by seperating out your different size disks into different disk groups?
I understand the benefits of using the same size disks in a diskgroup for Disk Failure Protection reasons, but is there a performance hit by having different size drives within a diskgroup?
Which brings up another question, what about different RPM Drives in the same diskgroup? My older 10k rpm drives are being replaced by 15k rpm drives. I have just been placing them back into the same diskgroup. Thoughts on different RPM speeds within a diskgroup?
Thanks
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Víctor Cespón
Honored Contributor
Solution

Re: EVA5000 and Performance

If a disk group has disks of different sizes, the bigger disks will contain more data so on average they will have to perform more I/O operations. This can lead to these drives saturating before the others.

Mixing 10K and 15 drives on a disk group has a similar effect, the 15K drives will do their I/O operations faster, the 10K drives will take a little longer. As the data is distributed among all drives, the slower or bussiest ones influence the maximum IOPS that the disk group can do.
Hermanator
Occasional Contributor

Re: EVA5000 and Performance

Vcespon, thank you for your response. There is not a lot I can do about the dfferent RPM Drives that I can think of. As our 10k RPM Drives go bad, they get replaced with 15k RPM drives, so I have no choice but to put them back into the same diskgroup. I guess I could wait until I get 8 bad ones and create a 15k rpm diskgroup with the 8, that could take awhile, but then that also takes away spindles from my original diskgroup.

Hmmm?
Uwe Zessin
Honored Contributor

Re: EVA5000 and Performance

Think about it in a positive way:

if you replace a 10k RPM disk drive with a 15k RPM one of the same size: the new disk processes I/Os faster, but it does not slow down the whole disk group. The more disks you replace, the faster I/Os get.

Don't understand me wrong:
I don't wish you many bad disk drives ;-)
.
Víctor Cespón
Honored Contributor

Re: EVA5000 and Performance

Don't create a small disk group.
It's better to have 20x10K + 10x15K for example, on a single disk group.