extremely slow write performance plaintext

[Mathieu AVILA]

Le 25/01/2011 07:21, Michael Monnerie a écrit :
> On Dienstag, 18. Januar 2011 Cory Coager wrote:
>> Also, I want to stress that I am only having performance issues with
>> one logical volume, the others seem fine.
> You're getting 40MB/s write speed and says that's fine? I get more
> performance from a single SATA desktop drive. Your setup seems to suck
> extremely somewhere.
>
> It already starts with your dd speed. I started it on a virtualized VM
> on an old, overloaded server and get:
>
> # dd if=/dev/zero of=test.dd bs=1k count=1M
> 1048576+0 Datensätze ein
> 1048576+0 Datensätze aus
> 1073741824 Bytes (1,1 GB) kopiert, 10,9992 s, 97,6 MB/s
>

I would say this is melted with cache hit, isn't it ? (although I agree 
it depends on the server's memory dedicated to FS cache)

A real cache hit on a real server would give me at least 500 MB/s 
(actually I get something around 1 GB/s)
When it starts to be disk-constrained, on a standard SATA disk, I get 
from 75 MB/s to 140 MB/s depending on the position of the AG I hit.


-- 
*Mathieu Avila*
IT & Integration Engineer
mathieu.avila at opencubetech.com

OpenCube Technologies http://www.opencubetech.com
Parc Technologique du Canal, 9 avenue de l'Europe
31520 Ramonville St Agne - FRANCE
Tel. : +33 (0) 561 285 606 - Fax : +33 (0) 561 285 635
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