topic Mixing Disk Speeds in Disk Enclosures

Mixing Disk Speeds

Geoff Marshall_1 — Wed, 02 Nov 2005 11:47:13 GMT

We have an existing ML370 server running a RAID 5 array with 3 x 18.2GB disks ( 10,000 rpm ).

One disk has failed and needs to be replaced. However we can only now buy 15,000 rpm disks new.

Will this work? Can we replace the faulty 10,000 rpm disk with a 15,000 rpm disk. What impact if any will this have on the existing array?

Re: Mixing Disk Speeds

Steven Clementi — Wed, 02 Nov 2005 11:50:46 GMT

Geoff:

Absolutely. The array should not care about the speed of the disk.

At the very least, the new disk may write a little faster, but performance should stay the same since the array is still running 10k drives.

Steven

Re: Mixing Disk Speeds

Ivan Ferreira — Wed, 02 Nov 2005 13:38:34 GMT

I just want to support Steven response. You can change the disk without problem, but the array will be limited to the 10K rpm disks speed. That means that your 15k rpm disk will run at 10k rpm maximum.

Re: Mixing Disk Speeds

Peter Mattei — Wed, 02 Nov 2005 14:40:10 GMT

Not exactly!
The new drive will run at 15k but to write a stripe the controller has to wait until all drives have written their part. So you will expereince almost the same performance as before; perhaps slightly faster.

Cheers
Peter

Re: Mixing Disk Speeds

Ivan Ferreira — Wed, 02 Nov 2005 15:06:25 GMT

Thanks Peter, my english is not good enough and is hard to explain some concepts to me. I just want to give to know that the disk "in the array context" will perform lower, because of the other disks. That is, exactly what you said.