Chris Cruft

I’ve been frustrated by tape drives for years.  They are the most finicky, unreliable, least-documented and most expensive components of most of the computer systems I have had the pleasure of administering.  I’m no longer an “up-to-date” sysadmin, but I still try to take care of my own stuff and, not surprisingly, tape drives still are the the top of my bitch list.

Today’s bitch is brought to you by stinit -a great idea that needs some love.

With stinit, you have a means of enforcing a configuration set on a device.  Since each tape drive (in the default Linux st configuration) is represented by four devices, you can easily define four different configuration modes for each drive.  Simply by using a different device (/dev/st0, /dev/st0a, /dev/st0l, /dev/st0m, for example) you can ensure your apps see the tape drive just so.

Unfortunately, stinit is weakly documented (just try the mode= syntax) and full of bugs that make tracking down simple errors costly.  Here’s the one I hit today…see if you can tell what the hell is wrong.

[Background: I have two tape drives connected to this server, one is a Compaq SuperDLT, the other an ancient Archive DDS drive for which I have no documentation]

[root@aprilia amanda]# stinit
Warning: No modes in definition for (’COMPAQ’, ‘SuperDLT1′, ”).
Can’t find defaults for tape number 1.
Initialized 1 tape device.

Hmmm…seems like I left out the modes in the definition of Compaq drive.  Let’s go to the file:

…
# Archive Python
manufacturer=ARCHIVE model=”Python 28388-XXX” {
        timeout=3600
}

# Compaq SuperDLT1
manufacturer=COMPAQ model=”SuperDLT1″ {
        timeout=3600
        mode1 blocksize=0
        mode2 blocksize=0
        mode3 blocksize=0
        mode4 blocksize=0
}

Puzzling.  The modes are clearly in there.  I try the stinit command again, this time with the verbose option:

[root@aprilia amanda]# stinit -v

stinit, processing tape 0
The manufacturer is ‘COMPAQ’, product is ‘SuperDLT1′, and revision ‘5F5F’.

stinit, processing tape 1
The manufacturer is ‘ARCHIVE’, product is ‘Python 28388-XXX’, and revision ‘4.45′.
Warning: No modes in definition for (’COMPAQ’, ‘SuperDLT1′, ”).
Can’t find defaults for tape number 1.
Initialized 1 tape device.

Interesting that the error message appears after stinit trys to initialize the Archive drive.  After a little googling, I find that an stinit bug was reported in the debian mailing lists (here) for the numbering of the modes.  On a hunch that the programmer couldn’t get his zero-based and one-based numbering straight for the tape drives either, I add a garbage mode for the Archive drive

# Archive Python
manufacturer=ARCHIVE model=”Python 28388-XXX” {
        timeout=3600
        mode1 blocksize=0
}

# Compaq SuperDLT1
manufacturer=COMPAQ model=”SuperDLT1″ {
        timeout=3600
        mode1 blocksize=0
        mode2 blocksize=0
        mode3 blocksize=0
        mode4 blocksize=0
}

…and ABRACADABRA, the problem goes away:

[root@aprilia amanda]# stinit
Initialized 2 tape devices.

This entry was posted on Friday, September 14th, 2007 at 10:07 and is filed under Linux, Hardware. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.