Re: Slow Soft-RAID 5 performance

[Rui Santos <rsantos@grupopie.com>]

Justin Piszcz wrote:
>
>
> On Wed, 18 Jul 2007, Rui Santos wrote:
>
>> Hi,
>>
>> I'm getting a strange slow performance behavior on a recently installed
>> Server. Here are the details:
>>
>> Server: Asus AS-TS500-E4A
>> Board: Asus DSBV-D (
>> http://uk.asus.com/products.aspx?l1=9&l2=39&l3=299&l4=0&model=1210&modelmenu=2
>>
>> )
>> Hard Drives: 3x Seagate ST3400620AS (
>> http://www.seagate.com/ww/v/index.jsp?vgnextoid=8eff99f4fa74c010VgnVCM100000dd04090aRCRD&locale=en-US
>>
>> )
>> I'm using the AHCI driver, although with ata_piix, the behavior is the
>> same. Here's some info about the AHCI controler:
>>
>
> With three disks, if everything was perfect yeah 120MB/s writes.  When
> I had started out with 4 raptors I was getting 164MB/s read and
> write.  By default with no optimizations you will not get good speed.
>
> With no optimizations with 10 raptors I get 180-200MB/s, with
> optimizations, 464MB/s write and 622MB/s read.
>
> 1. Use XFS if you wan't speed.
> 2. Use 128k, 256k or 1MiB chunk size.
> 3. Use 8192k, 16384k stripe_cache_size.
> 4. Use 65536 readahead size.
>
> These are only some of the optimizations I use.
Thank you for your reply.

I've used: 1) xfs, 2) 256k, 3) 16384k and 4) 65536 readahead.

Also tryed ext3 with --stride option. The speed is just a bit slower...

I can get ~100MB/sec.

The hardware is capable of doing better tough...

Thanks for your help.
>
> Justin.
Rui Santos

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