CERC ATA100/4ch problem

Toni Riekkinen list-toni at ntg.fi
Fri Oct 29 07:18:01 CDT 2004

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.


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,


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