Re: Performance issues with Areca 1680 SAS Controllers

[Andrew Morton <akpm@linux-foundation.org>]

(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!