PE4600 and Red Hat Questions

Abe Hayhurst abe at
Fri Jun 21 16:55:01 CDT 2002

What tools should I use to test the performance of the RAID when I change
the parameters? Do they come on the RH7.3 CDs? If not, where can I get them?

-----Original Message-----
From: Seth Mos [mailto:knuffie at]
Sent: Friday, June 21, 2002 4:21 PM
To: Arjan van de Ven; Abe Hayhurst
Cc: linux-poweredge at
Subject: Re: PE4600 and Red Hat Questions

At 16:35 21-6-2002 -0400, Arjan van de Ven wrote:

>for raid0/1 I'd recommend 64K to 128Kb... smaller is worse generally.
>Playing with the caching settings (and readahead) is worth it, the optimal
>settings for these very much depends on the workload

128KB works well in combo with both the 10KRPM and 15KRPM disks.
I tested this on a PERC3/DC in a 2550 with raid10. Larger gives you better
sequential throughput.

> > My setup will be a PERC3/DC with 4 10,000 RPM drives on each SCSI
> > for a total of 8 10,000 RPM drives. I was planning on doing RAID 10
> > from what I had read on Dell's website this would give me the best
> > performance. My goal is maximum MB/sec. The RAID will be used for file
> > sharing large (50 - 500 MB) files. So the goal would be maximizing
> > for sequential reads and writes. Since an individual drive can push 25 -
> > MB/sec I was hoping to achieve 100 - 120 MB/sec.
>120Mb/sec will be a nice chalange versus the PCI bandwidth.
>Note that pure RAID0 will be faster than RAID10 for single threaded use.

It's a 64Bit/66Mhz bus/card so it's more like 533MB/s :)
Raid 10 is fastest in reading and writing at the expense of some extra
disks. It's also low overhead on the raid controller. The PERC3/DC isn't
the most powerfull raid controller.
If you can spare the money the PERC3/QC should be a faster choice even when
you are not using the other channels. Although I am not sure this affects
the raid 10 performance.


It might just be your lucky day, if you only knew.

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