Re: Performance issues with Areca 1680 SAS Controllers

["Pasi Kärkkäinen" <pasik@iki.fi>]

On Thu, Nov 20, 2008 at 03:39:40PM +0800, Nick Cheng wrote:
> Hi Michael,
> I will get around handling your issue.
> Thanks for your kindly patience,
> 

Hello,

Was this issue resolved? I'm seeing similar behaviour.. I think it's related
to flushing the controller cache?

Waiting a while (after the disk leds stop blinking) performance is back to
normal.. 

-- Pasi

> -----Original Message-----
> From: Andrew Morton [mailto:akpm@linux-foundation.org] 
> Sent: Thursday, November 20, 2008 9:18 AM
> To: Michael Fuckner
> Cc: linux-kernel@vger.kernel.org; linux-scsi@vger.kernel.org; Nick Cheng;
> Erich Chen
> Subject: Re: Performance issues with Areca 1680 SAS Controllers
> 
> (cc's added)
> 
> On Wed, 19 Nov 2008 13:16:56 +0100
> Michael Fuckner <michael@fuckner.net> wrote:
> 
> > Hi,
> > 
> > I am using an Areca 1680-SAS-Controller with 16 SAS-HDD (Seagate 1TB
> > ST31000640SS). I set up a Raid6 with all 16 disks and formatted it with
> > XFS. The Controller has 512MB RAM and a BBU. The OS is installed to
> > another disk attached to the onboard AHCI controller.
> > 
> > After doing some IO, the areca raidset is slower compared to the rate 
> > directly
> > after boot.
> > 
> > 
> > [root@storage ~]# dd if=/dev/sdb1 of=/dev/null bs=1M count=50k
> iflag=direct
> > 51200+0 records in
> > 51200+0 records out
> > 53687091200 bytes (54 GB) copied, 59.6494 seconds, 900 MB/s
> > [root@storage ~]# mount /dev/sdb1 /data
> > [root@storage ~]# cd /data/
> > [root@storage data]# ./iozone -i 0 -i 1 -s 32g -r 16m -S 6144 -t 8 -+r
> > -o  >raid6_sync_t8.log
> > [root@storage data]# cd
> > [root@storage ~]# umount /data/
> > [root@storage ~]# dd if=/dev/sdb1 of=/dev/null bs=1M count=50k
> iflag=direct
> > 51200+0 records in
> > 51200+0 records out
> > 53687091200 bytes (54 GB) copied, 76.4036 seconds, 703 MB/s
> > 
> > I tested different Versions of Linux (Centos 5.2, OpenSUSE 11, Debian
> > Lenny) and Vanilla kernels 2.6.22-2.6.27, all show this behaviour.
> > 
> > Idea why the device slows down after IO- or better: how to keep the high
> > rate? Is this reproducible foer Areca SATA Controllers (Type 11XX and
> 12XX)
> > 
> > Regards,
> >    Michael!
> 
> --
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