Re: Disk performance problem
On Thu, 25 Feb 2010 11:48:27 +0200
Veli Cakmak <veli.linux@gmail.com> wrote:
> Dear Friends;
>
> I have servers which contain SATA disks and SAS disks. I was testing the
> speed of writing on these servers and I recognized that SAS 10.000 disks
> much more slowly than the SATA 7200. What do you think about this slowness?
> What are the reasons of this slowness?
>
>
>
> Thank you for your help.
>
>
>
>
>
> I am giving the below rates (values) which I took from my test (from my
> comparisons between SAS 10.000 and SATA 7200);
>
>
>
>
>
> dd if=/dev/zero of=bigfile.txt bs=1024 count=1000000 when this comment was
> run in SAS disk server, I took this output(10.000 rpm)
>
> (a new server,2 CPU 8 core and 8 gb ram)
>
> 1000000+0 records in
>
> 1000000+0 records out
>
> 1024000000 bytes (1.0 GB) copied, 12.9662 s, 79.0 MB/s (I have not used this
> server yet) (hw raid1)
Your testchunk is smaller than your RAM, so you test mainly the
performance of your cache. You also have different RAID-configurations.
Try these tests again with 100GB data, at least 3 times with every
disk you want to test. At the same server. Then you may start comparing
results.
Dirk.
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