[CentOS-virt] SATA vs RAID5 vs VMware

[Rich]

I have been using a 3ware 9690se sata card with raid5.  I have been running
Centos using xen and have had no problems.
I wrote my virtual machines to the raw raid5 drive.  Its seems to have
worked fine for me.

On Thu, Sep 24, 2009 at 9:18 PM, Philip Gwyn <liste at artware.qc.ca> wrote:

> Hello,
>
> I have strange behaviour on a server that I can't get a handle on.  I have
> a
> reasonably powerful server running VMware server 1.0.4-56528.  It has a
> RAID5
> build with mdadm on 5 SATA drives.  Masses of ram and 2 XEON CPUs.  But it
> stutters.
>
> Example : fire up vi, press and keep finger on i.  After filling 2-3 lines,
> the
> display is stopped for 2-12 seconds.  Then they continue.  This happens
> even on
> the host OS, at the console.
>
> Host system running CentOS 5.2 x86-64:
>
>  CPU : 2x Xeon E5430 @ 2.66GHz
>  RAM : 24GB
>  Mobo : DSBV-DX
>   HD : 5 x SATA ST3750330AS 750GB in RAID5
>
> There are 5 VMs, detailed at http://www.awale.qc.ca/vmware/stj1.txt to
> make
> this mail shorter.
>
> Seems to me this system should be more then adequate to handle the load.
>
> This is what vmstat on the host looks like when the server is "unhappy" :
>   http://www.awale.qc.ca/vmware/vmstat.txt
> Spending a lot of time in 'wa', but 'bo' and 'bi' are miniscule.
>
> The problem seems like a disk problem.  I grow to suspect that SATA isn't
> ready
> for the big time.  I also grow to dislike RAID5.
>
> Questions :
>
> - Anyone have a clue or other on how to track down my bottle neck?
>
> - SATA NCQ is limited to 15 queue depth.  Is this per-SATA-port or
>  per-SATA-chip? Or does this question make no sense?
>
> - I realise there are more recent versions of CentOS out.  Are there
> specific
>  items in the changelogs that would affect my problem?
>
> Thank you for any help,
>
> -Philip
>
>
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