the performance of SAS is not better than SCSI in FreeBSD, WHY?
Tzu-Hua Wang
biogary at gmail.com
Thu Apr 12 16:42:13 UTC 2007
Hi:
When using 'dmesg' command, it shows that
da0 at ciss0 bus 0 target 0 lun 0
da0: <COMPAQ RAID 0 VOLUME OK> Fixed Direct Access SCSI-0 device
da0: 135.168MB/s transfers
da0: 419946MB (860051248 512 byte sectors: 255H 32S/T 65535C)
Oh, my goodness. My SAS HD is only the SCSI-0 device.
I think this is the major reason.
Why? Can you give me a hand? Problem of configuration on the RAID Card?
I am sorry, I am really new to the RAID system.
Thanks
2007/4/11, Ivan Voras <ivoras at fer.hr>:
>
> Tzu-Hua Wang wrote:
>
> > Generally, the performace of SAS in FreeBSD is far worse than SCSI in
> > FreeBSD.
> > Is it normal? How can I do to improve the performance of SAS HD in
> FreeBSD?
>
> There's a huge number of possible reasons - unless you're testing the
> same controller (I think there exist SAS+SCSI controllers, I might be
> wrong), you can't conclude that the SAS interface is less supported.
>
> For what it's worth, I've got approximately the same numbers on DL380
> G5, but I've attributed them to 2.5" small form factor drives.
>
> 2x 2.5" 10k RPM, CISS hw RAID1 2x 3.5", 7.5k RPM, soft RAID1
> Full stroke 3.863 ms 5.942 ms
> Half stroke 3.929 ms 6.186 ms
> Quarter stroke 3.998 ms 5.700 ms
> Short forward 3.889 ms 4.060 ms
> Short backward 4.715 ms 4.748 ms
> Seqential outer 1.011 ms 0.167 ms
> Sequential inner 1.013 ms 0.177 ms
> Read transfer, outside 43.6 MB/s 61.2 MB/s
> Read transfer, middle 38.8 MB/s 54.8 MB/s
> Read transfer, inside 32.8 MB/s 34.9 MB/s
>
> The 3.5" drives were SATA in a different machine (Dell's). It might be
> that the CISS driver is unreasonably slow, which is kind of possible
> given the suspicious lower bound of about 1 ms in seeks. Maybe something
> is throttling the I/O rate?
>
>
>
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