[CentOS] Centos 5.6 3ware raid 5

Wed Feb 8 18:59:31 UTC 2012
Timo Neuvonen <timo-news at tee-en.net>

> Hi, I've seen comments about the poor performance of these cards with
> raid 5 configs. I have an old card with 3 x 500G IDE drives connected in
> raid 5 and I'm getting around 10mb/s write performance. :-(
> I'm seeing high iowait figures at times and associated very high cpu
> load average figures, probably because, under load, everything is
> stacked up waiting for the disks to actually do something.
> A non-raid sata disk in the same machine manages 70mb/s
> Does anyone know what the performance is like if I used the 3ware just
> as an IDE controller? I could then switch to software raid5?

Since you have IDE drives, you obviously have 3ware 7506 card, which is very 
old. I'm not sure when it was released but that might have been before Y2k. 
Anyway, at least 10 years ago. It's not fair to talk about "3ware card 
performance" without specifying the card when you mean that old card. Their 
9650/9750/9690 of today are more than one generation newer, there has been 
8xxx and 9000/9500 series that also are obsolete now.

If yoy use 3 drives and configure 7506 as a transparent controller for each 
of them, and set up a software raid, then all the drives are behind a single 
pci slot, which also could be a bottleneck if you don't have a 64-bit pci 

That said, I seriously recommend jumping to something more up-to-date 
technology. But don't expect that newer 3ware cards were even close to that