Sorry for answering again, accidently hit send while not finished
to compare an LTO4 drive with an Ultra320 controller
I get around 55MB/sec
my guess is that the LTO3 drive should deliver around 30-40MB/sec
with the right controller (ultra320).
(pay note to that there usually are 2 models, a fast and slow one, from
each vendor)
trying to remember back when using a 2940UW host adapter with a UW drive.
I seem to remember to get around 10MB/sec out of the drive
so 8.8MB/sec does seem like it's what you can get out of the controller.
(I could remember wrong)
cheers
Carsten
On 2012-10-18 21:02, Wolfgang Denk wrote:
> Hello,
>
> apologies in advance - this may be a bit off topic, but I guess I find
> most experts for such a problem on this list...
>
>
> I see very poor performance with HP Ultrium LTO3 drive, which is
> attached over SCSI to a Linux box (using a Adaptec 2940 Ultra SCSI
> adapter). It seems I cannot get more than about 8.8 MBytes/s for
> either writing to or reading from the drive.
>
> Looking around, I see this information in /proc/scsi/aic7xxx/3 :
>
> ...
> Target 5 Negotiation Settings
> User: 40.000MB/s transfers (20.000MHz, offset 127, 16bit)
> Goal: 10.000MB/s transfers (10.000MHz, offset 15)
> Curr: 10.000MB/s transfers (10.000MHz, offset 15)
> Channel A Target 5 Lun 0 Settings
> Commands Queued 20
> Commands Active 0
> Command Openings 1
> Max Tagged Openings 4
> Device Queue Frozen Count 0
> ...
>
> Am I understanding this correctly that the SCSI adapter is set to
> 10 MB/s transfers only? That would certainly expolain the transfer
> rates I'm observing...
>
> Is there any way to tweak these settings in Linux? I alreay checked
> in the SCSI adapter's BIOS settings, but there are no indications for
> auch a limitation.
>
> [Yes, I am aware that the Adaptec 2940 is not exactly new. But I
> should get more than 8.8 MB/s out of it, should I not?]
>
> Any help welcome. Thanks in advance.
>
> Best regards,
>
> Wolfgang Denk
>
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