Subject: Re: kern/29369
To: None <>
From: Frank Kardel <Frank.Kardel@Acrys.COM>
List: netbsd-bugs
Date: 03/11/2005 09:58:30 wrote:

>Synopsis: ahc driver cannot handle HP LTO 2-SCSI drive - SCB timeout / BDR -> hang/unusable -> REBOOT needed
>State-Changed-From-To: open->feedback
>State-Changed-When: Thu, 10 Mar 2005 13:43:48 -0500
>Chris Badura said the following:
>So, I've looked at this.  I think the 29369 PR is not fine.  There are only
>only 2 scsi tape firmware manufacturers and probably only 1 LTO firmware
>vendor.  The driver should detect that the device is a LTO drive (maybe by
>capacity as the other QIC_* drives too) and clear ST_2FM_AT_EOD in that
>case too.
I already tried clearing  ST_2FM_AT_EOD when this drive is detected. 
This strategy fails as then
the blank check condition leads to an EIO to the application. Just 
pretending it is a QIC tape
won't satisfy all tests that the bacula btape program does to ensure 
proper communication
with the drive. It helped to handle blank checks just like non QIC 
tapes. After that the driver
exhibited a compatible handling and response of the drive. Maybe I am 
missing something here
but just turning of ST_2FM_AT_EOD didn't cut it with the drives default 

>To be more correct the drive should determine this from the EOD and SOCF
>fields in the device's Device Configuration Page which has been the standard
>way since roughly 1991.  *sigh*
I just looked into the standard. Though I cannot say that it answers all 
my questions on what configurations
result in a reliable and correct operation it'll help somewhat.
It looks to me that the drive should be but into a mode where 2 FMs are 
recognized to stop reading data into
the buffer (does that mean an EOM condition or just stop the transfer?). 
Setting RSmk should enable
us to find track the position while doing an "mt eom". How wrong am I here?
All in all it should be doable.

>Frank, what do you think? Is that something you'd be interested doing?
Interested yes. It is primarily a logistical challenge. The drive is 
backing up our company data and such a drive is not really
in the price range to have a spare one at home for testing. And as the 
st drive does not seem to be loadable
testing this would require a few reboots (or can XEN support access to 
the tape drive?). These reboots would
hit the main production file server - I am a bit reluctant to do that 
for hopefully understandable reasons.
But it seems that I am so far the only one running that drive with 
NetBSD. Does anyone know whether
other projects have support for LTO drives in their st drivers ?
I currently have a solution, so if I would go through implementing the 
"right thing(tm)" it may take a while
given the environment. So if someone fixes the ahc/scsi-timeout issue 
I'll take a stab at supporting LTO drives.


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