Mixing 10k and 7.2k RPM on same controller

[Jonas Back_2]

Have a DL380G5 with E200i (128MB BBWC) and the following drive config:
C: 2*72GB 10k SAS RAID1
D: 2*300GB 10k SAS RAID1

We now need to add some cheap storage for archving data:
E: 4*500GB RAID5

The cheapest alternative are the 500GB 7.2k SATA drives. As I understand it, you can mix types as long as they are not in the same array.

But what about the 10k / 7.2k RPM mix? Will this affect performance of the 10k disks? Have in mind that the 7.2k array will more or less be idle except for an hour during the night when we archive files to it. We will hardly ever read from it.

And maybe someone could clarify if we would connect these 4 7.2k drives to a seperate channel on the internal controller or an additional controller, would that make a difference?

[gregersenj · Accepted solution]

SATA / SAS is a single device point to point protocol.
So each drive got it's own wires.

It won't caurse any performance issue on the 10K RPM drives.

Yes you can put it on the same controller. No problem.

No you can't put them in the same array.


What you should consider. is if you got many write operations to the SATA drives.
Being slow drives and RAID 5 (The write penalty).
That could have a performance impact.
But that depends on the load of the system.
If so, an extra Smart Array could solve that.

BR
/jag

[Jonas Back_2]

A very detailed response - thank you very much.

So it's more if you mix 10k and 15k SAS disks in the same array when you face less performance?

[gregersenj]

The 10K drive will perform slower than the 15K drive.

A RAID with 15K drives only will perform better than a RAID with mixed drives.

A RAID with mixed drives may perform a little better than a RAID with 10K drives only.

Putting a 15K drive in a 10K RAID, will not reduce performance.