ratio of latency between SAS and SATA disks

[mdvillanueva]

Hi Experts,

I need advise on gauging performance between SAS and SATA disks   

I read that a 7.5K SATA has about 4ms latency and a 15k SAS 2ms latency.

Using that ratio, is it safe to say that if:

* a given volume that has a 6ms latency on a 48 disks 15k SAS aggregate was to be moved on a 48 disks 7.5k SATA aggregate, that the latency would double to 12 ms?

* and if that same volume is to be moved to a 24disks 7.5k SATA aggregate, that the latency would quadruple to 24ms?

Thanks,

Maico

[jorisv]

not really, the key is latency at a given amount (of type) of iops. But even understanding the differences in disk performance between sas and sata might do you little good. NetApp systems will accelerate basic disk performance in various ways depending on the load you give it. Your best bet would be to use NetApp sizer tools to help model the load and plot that on different configurations. You can even input live measurements as the basis of such a sizing!