an Adaptec 2940 is usually only a SCSI-II device with 10MB/Sec
the 2940UW performs 40MB/sec
these are maximum bus transfers
If you haven't made any special modifications to the driver/kernel, then
linux uses the fastest speed possible delivered by the restrictions of
the host adapter.
going alittle off-topic here myself.
the LTO3 drive is afair an Ultra320 (320MB/sec)
otherwise it could be an Ultra160
pressing CTRL-A when the SCSI bios tells you to, you should be able to
set transferspeeds to 40MB/sec in one of the menues.
though performance will still be bad.
you should have around 2Gig pr min with the LTO3 drive if it's the fast
model
replacing the SCSI host adapter to the Adaptec Ultra 160 or 320 models
will give a much better performance, the 2940 is from last millenia
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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