[Gllug] Centos 5.6 3ware raid 5

[James Courtier-Dutton]

On 8 February 2012 12:24, Ken Smith <kens at kensnet.org> wrote:
> Hi, I didn't get any response on the Centos list so I thought I'd ask here
> for any experience with using a 3ware raid card as a simple IDE interface.
>
> 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?
>

If it uses the megaraid driver, (not sure exactly what it is called)
on a old Linux kernel version, then you might get problems.
I had a number of problems with HP DL servers. More up to date Linux
kernels use a new driver, different name, that does not seem to have
the same problems.
The problems I ran into where the controller pausing sometimes and
failing to process requests. The problems were mainly with a
combination of tape drives and disks.
The newer driver, of a different name, fixed the problems.
So, I would ask, which Linux kernel driver are you using.
The output of "lspci" and "lsmod" would help.

Kind Regards

James
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