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[转载]forcing transfer rate & offset

[转载]forcing transfer rate & offset

文章作者:aic7xxx
信息来源:MARC

I am not an expert on any of this, so please keep the replies coming back to
the list, it is highly probable some one else will have better answers.

Lars A Anderson wrote:
>
> i have a unique scsi peripheral - VLDS tape drive with a scsi 1
> personality card. i can get it to respond to mt commands: status,
> rewind, offl, but i cannot transfer data. the user manual says it will
> ONLY communicate at 5MHz with a REQ/ACQ offset of 5.

Are you sure the drive is actually fully SCSI 1?
Considering the company address you are sending from I ask because you might
be working with a drive from a tactical system, and I have seen too many of
the older "SCSI 1" drives be actually ALMOST SCSI 1, and I expect the
aic7xxx card and driver conform exactly to the SCSI 1 spec when talking to
something that claims SCSI 1 compliance.

> no matter how i try
> i cannot get my 2930CU under 2.4.31 and aic7xxx v6.2.36 to come up with
> these settings. it always reports (via cat /proc/scsi/aic7xxx/1 )
>
> > Target 6 Negotiation Settings
> >      User: 3.300MB/s transfers
> >      Goal: 3.300MB/s transfers
> >      Curr: 3.300MB/s transfers
> >      Channel A Target 6 Lun 0 Settings
> >            Commands Queued 4
> >            Commands Active 0
> >            Command Openings 1
> >            Max Tagged Openings 0
> >            Device Queue Frozen Count 0

you might also try setting
aic7xxx=verbose.global_tag_depth:1
when you load the module, to get more debug data in syslog, and make sure
the card will only attempt to have 1 command for the drive at one time (just
being paranoid).

>
> and dd if=/dev/st1 of=/scratch/test  always fails.

If you have a tape that you know does not have data you need on it, I would
suggest first:

dd if=/dev/urandom  of=/tmp/somejunk bs=1 count=1024k
dd if=/tmp/somejunk of=/dev/st1

and then try to read back, because IIRC if there is no data on the tape (or
data the tape drive can't read) you will get nothing or an error from the dd
doing the read.

>
> i have tried messing with the card bios, aic7xxx module parameters, st
> module parameters, i tried aic7xxx_old, i am at a loss.

you should probably make sure the card bios is back at a frequency at/above
5MHz (10MB/s, IIRC the card bios displays its settings in MB/s).
did you try the ASYN setting in the card bios too?

All of this information comes with out warranty or intention of Gov.
contractor direction.
--
Todd Denniston
Crane Division, Naval Surface Warfare Center (NSWC Crane)
Harnessing the Power of Technology for the Warfighter
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