[nycbug-talk] tape drive woes
Thu Feb 3 23:11:27 EST 2005
On Thu, Feb 03, 2005 at 07:46:48PM -0500, Dan Langille wrote:
> I was given a DDS-4 tape drive at BSDCan last May. Last night, it
> started acting up.
> The following gives the following:
> mt -f /dev/sa0 status => http://www.langille.org/tmp/ach-dumps.txt
I get that (SCSI bus resets) with my DDS-1 and -2 drives as well and
I've seen it with DDS-3 drives.
> It's not the card (I hooked up a SCSI disk and newfs'd it, just
> fine). It's not the cable (I tried another one, but not a new one).
Right. In my case, different cards and cables didn't help. A new tape
(as in brand new) helped, sometimes, for a short time.
I suspect that the drive needs cleaning. DDS drives need cleaning like a
baby needs changing. I typically run a cleaner tape through after 2 tape
runs now and I *still* encounter those errors, though at a significantly
Putting the drive on it's on SCSI controller helps, because when it
/does/ happen it doesn't freak out all the other devices on the bus.
The traditional wisdom with bus resets is that it's due to exceeding the
SCSI specifications in some manner: poor termination, too-long cable,
that sort of thing. I've have luck with a DEC StorageWorks JBOD tower
that used to bus reset like a mad banshee simply by telling the
controller to run it at a slower rate -- a more robust SCSI bus results
from the "easier" specifications. Since this particular SCSI controller
only "auto-detects" SCSI settings and won't allow me override them in
it's "BIOS", I wrote a /etc/rc.d script that manually forces the devices
down one speed notch just before fsck kicks in (which would cause bus
resets like crazy). The basic idea is this:
camcontrol negotiate da0 -R10 -q -a
I'm simply moving the bus from 20MHz to 10MHz which, at 16 bits wide,
moves me from 40MB/s to 20MB/s. That's more than fast enough for the
drives I have in the JBOD (which aren't ever accessed simultaneously
with the use I've put them to) and all top out at about 12MB/s anyway).
It's worth a try, especially considering that DDS-4 doesn't write fast
enough to need the full 40MB/s of Ultrawide SCSI.
> So I'm looking at buying a Seagate DDS-4 Scorpion STD2401LW
> <http://tinyurl.com/5g6ga> for CAD$650 (+taxes).
> Anyone got one and can tell stories about it?
No, but I also had no idea that they'd gotten so cheap. *Damn*, that's
> Please note: This is not the thread for saying tape is crap, DAT is
> crap, use HDD, use DLT, etc... Unless of course, you're prepared to
> give me the hardware and the media. Then I'm prepared to listen. :)
And if anyone is handing out tape hardware, I'm willing to cover the
cost of shipping if it's to help out freshports.org.
Fsck, either way I'm screwed. -- petro
Now *that* is the Sysadmin's motto. -- Peter da Silva
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