[CentOS-virt] SATA vs RAID5 vs VMware

Fri Sep 25 01:46:53 UTC 2009
Luke S Crawford <lsc at prgmr.com>

Philip Gwyn <liste at artware.qc.ca> writes:

> 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.  


> 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.

Personally, I will use RAID5, and I will use SATA, but I will not use 
SATA with RAID5 except in 'tape replacement' roles.  The weak bits of 
RAID5 (read/ write cycle on sub-stripe writes) are often exasterbated 
by the weak bits of SATA (slow seek time, slow rotational speed)  
creating a perfect storm of suck.

Not to say that's your primary problem.

Actually, it sounds a whole lot like the problems I get with xen on 
heavily used servers, if I don't assign a core exclusively to the dom0 
(or at least give it a very high priority.)  But I have little knowledge
of or experience with VMware, so I don't know if you have a 
similar problem.  

Luke S. Crawford
http://prgmr.com/xen/         -   Hosting for the technically adept
http://nostarch.com/xen.htm   -   We don't assume you are stupid.