Friday, May 16, 2008

SAS vs. SATA

I use Solaris zones a lot.

We've got a number of X2200s, in two variants. Some just run web front ends, and are fitted with SATA drives (once running, the only disk activity is the web server logs); the database back-ends have SAS drives.

OK, so the SAS drives are expected to be a bit quicker - we did get them for that purpose. Based solely on the rotational speed, there's about a factor of 2 difference in performance.

However, if you take zone creation time as a metric, the performance difference is rather larger than a factor of 4. Something else makes the SAS drives fly and the SATA drives crawl.

2 comments:

Ben said...

I've noticed this too.

The seek times are much better on SAS drives (especially 2.5" SAS drives) than SATA drives, so isn't that going to be more of a factor than rotational speed? Of course, the rotational speed helps to make the seeks faster, but raw data transfer isn't going to have much effect for zone creation.

zdzichuBG said...

My shot: TCQ on SAS drives and lack of NCQ on SATA ones.