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Disk Enclosures
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Mixing 10k and 15k disks

toomas_aas
Frequent Advisor

Mixing 10k and 15k disks

Hello!

I have a RAID5 array currently consisting of (4) 146GB 10k rpm U320 hard drives, living on Smart Array 6i controller inside a Proliant DL380G4 server. I'm planning to soon move the array to MSA1500cs/MSA30 system and add 8 more HDDs. Is it safe to add 15k rpm drives to existing array of 10k rpm drives and is there any performance benefit (at least theoretically)? My own thinking says it should be reasonable move, but what do the experts think?
5 REPLIES
Jefferson Humber
Honored Contributor

Re: Mixing 10k and 15k disks

Hi,

8 more HDD into the same RAID5 array, giving 12 disks in total ?

Sure it can be done, but the array will only work at the speed of the 10K HDD's. When mixing, the slowest/smallest member's characteristics is always inherited to all members in the array.

Hope this helps,

Jeff
I like a clean bowl & Never go with the zero
toomas_aas
Frequent Advisor

Re: Mixing 10k and 15k disks

Isn't it the case that 10k drives only slow down these reads/writes where I/O is actually done to/from these drives? In case of RAID5 array of 12 drives, where 1/4 of the drives are 10k and 3/4 are 15k I'd imagine that at least *some* array access is done so that it doesn't involve the 10k drives at all.

If that were true, mixed array would still be a little bit faster? Just a little bit? Pleease? ;)
Uwe Zessin
Honored Contributor

Re: Mixing 10k and 15k disks

A 15 kRPM disk drive will not magically rotate at 10 kRPM when it is mixed - that is not possible, so the entire array can be a bit faster.
.
F Verschuren
Esteemed Contributor

Re: Mixing 10k and 15k disks

15 rpm disk will create more head,
Whene we upgrades disks in the old autoraid, we alsow hat to change the fans...
please chack if you fans can take on the head...
toomas_aas
Frequent Advisor

Re: Mixing 10k and 15k disks

At least HP themselves claim that this is not a problem with their drives:

http://h18004.www1.hp.com/products/servers/proliantstorage/drives-enclosures/hotplug-ultra3/questionsanswers.html#3

Was your experience with HP drives?