CERC ATA100/4ch problem

[Toni Riekkinen]

Joan Josep Ordinas Rosa wrote:
> I have a PowerEdge 1600SC with two CPUs, 3GB RAM, 4 (120MB) IDE disks 
> and the RAID controller CERC ATA100/4ch using RAID 5.
> 
> The operating system is Linux server 2.4.20-9smp and the BIOS, RAID 
> firmware and megaraid2.o driver are the latests.
> 
> This is my problem:
> 
> 1. The disks are slow:
>  >#hdparm -t /dev/sda
>  >/dev/sda:
>  > Timing buffered disk reads:  64 MB in  3.02 seconds = 21.19 MB/sec

I had same problems with CERC ATA100 controller. I tried megaraid 1.18 
and megaraid2 drivers, different variations on read/write/cache 
policies, raising max_sectors_per_io from 128 -> 1024, etc. Almost 
everything suggested here at mailing list.

As far as I know, there is no solution for bad performance with this 
controller and RAID 5. I strongly suggest using RAID 10 instead of RAID 
5, if possible.

http://lists.us.dell.com/pipermail/linux-poweredge/2003-December/017320.html

You can search archives about this issue, there has been some other threads.

BTW. hdparm and dd (at least without sync) are not reliable for 
measuring disk/io speed, try using bonnie++.

Best regards,

++Toni