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5. Optical jukeboxes

I have no experience with optical jukeboxes with Linux!!!! I have had experiences with Optical jukeboxes under HP-UX. In this setup the the jukebox had a SCSI address of it's own. Each slot in the jukebox had an associated LUN number. A device name was assigned for each disk slot A side and B side. The mount command was run against the appropriate device name. I had a jukebox with just one drive and 16 optical disk slots - 20 Gig. I thought it was going to be a real hassle to write a disk mount manager to share this drive among users until I discovered you can mount as many disk as you want and the jukebox driver takes care of arbitration - what a nice feature. Granted, you only want archive type data here and your overall system configuration to be such that not too many processes will be accessing the jukebox at the same time. The disk spin down, carriage load, carriage move, carriage unload, carriage move to the next disk, carriage next disk load, carriage move, optical drive load, and spin up takes about 12 seconds - "seek-from-hell".

5.1 Maxoptix 520 - Zed Shaw

shawz@imap1.asu.edu

Zed's Original E-Mail - Feb 13 1998

Hi,
   
I was reading your howto (a life saver, thanks) and I was wondering what
kind of jukebox you were running?  I have a Maxoptix 520 Jukebox (20
disks at 2.6G each, nice!) and I would like to connect it to a Linux box
and serve the drives up to my users, but I'm having problems accessing
the individual drives.   Currently I can only access the two drives and
something called MAXLYB which I think is a controller device of some
sort.
   
Basically, I'm wondering if the jukebox you had was the same or similar
and how you set it up.  I know that you did it under HP-UX, but any help
right now would be nice.  Hey, I'll even let you log into my linux
server if you want to take a look at the jukebox and see what it does.
You can't beat 52Gig of storage!

Anyway, I'd really appreciate your help.


Zed A. Shaw
Application Systems Analyst
Arizona State University

Correspondence with Zed on Mon, 16 Feb 1998:

> It sounds like your Maxoptix 520 is a jukebox with two physical disk.
Yep, that's the one.

> 
> All jukeboxes have a carriage controller. This is probably your MAXLYB
> device.
> ...

What I've come to find out is that Maxoptix is pretty stingy when it 
comes to drivers.  Apparently, they don't make driver software for any of 
their Jukebox carriage controller interfaces!  I don't know how some of 
these companies stay in business.  I'm going to pester them again soon, 
but you are right, this thing will need a carriage controller driver to 
operate.  The cool thing is that this MX520 (that's the model number of 
the juke) emulates a whole slew of other carriage controllers, so maybe 
one of those other guys has a driver.  I'll be looking into that too.


> 
> You might want to get a-hold of Maxoptix and see if they have a install
> package for your linux kernel version. If not ask them for the programmers
> specification for the carriage controller and maybe we can write one!
> 

Hey, if I can't find any driver software, and I can convince Maxoptix to 
give me the specs, I'd be more than glad to write a driver.  I'd could 
sure use the help too since I haven't got enough time to do it on my 
own.  Also, do you know of anyone else doing this that we might be able 
to hack off of?


> Any information you find, let me know and we will roll the information
> into the Optical HOWTO, acknowledgments of course!
> 

Sure, but let me get some new information first.  So far things are 
looking pretty bleak.

> 
> >Basically, I'm wondering if the jukebox you had was the same or similar
> >and how you set it up.  I know that you did it under HP-UX, but any help
> >right now would be nice.  Hey, I'll even let you log into my linux
> >server if you want to take a look at the jukebox and see what it does.
> >You can't beat 52Gig of storage!
> 
> Nice. At home I can use PPP to mount my 84 platter HP-UX jukebox.
> It's slow though - I wish I had it at home.

Oh, I don't have this thing at home.  There's no way I could afford the 
$30,000 my boss paid for this thing.  But he's stuck with it and has had 
it sitting around collecting dust for a year, so he's letting me play 
with it and try to find a use for it.

I'll get back with you when I have some more information.  It should be 
sometime this week when I find out if I can get it to work or not.

Zed

5.2 Changer Devices - Jon Gerdes

Skip

Please find some guff on MO drives and SCSI agony ...

Note that the Changer software mentioned should work for virtually any
changer :-)

Now back to dreaming of cheap highbandwidth inet connections for home
use.  British Telecom really get on my !"£***&

Cheers
Jon Gerdes



Some notes on firing up SCSI changer support for a Magneto Optical jukebox
using "scsi-changer" 
==============================================================

LSM entry from distribution used:
Title:          scsi-changer
Version:        0.14
Entered-date:   9 May 1998
Description:    SCSI Media Changer device driver (for the robot mechanism
of MO/CD Jukeboxes, tape libraries, ...).
autofs support included.  This is a BETA version.
Keywords:       scsi jukebox changer driver
Author:         Gerd Knorr <kraxel@cs.tu-berlin.de>
Maintained-by:  Gerd Knorr <kraxel@cs.tu-berlin.de>
Primary-site:   sunsite.unc.edu /pub/Linux/kernel/patches/scsi
22kB scsi-changer-0.14.tar.gz
627  scsi-changer.lsm
Alternate-site: none
Original-site:  none
Platform:       Linux
Copying-policy: GNU GPL
===============================================================
Latest version from here:

http://www.in-berlin.de/User/kraxel/linux.html

Tested on:
HP SurestoreOptical 40fx (1 drive 15x2.4Gb MO disks)
Adaptec 1520B (dodgy ISA 10MBs-1 SCSI II card) 
Linux Mandrake 6.1
Kernel 2.2.13 and 2.2.14

tar -xzvf changer-0.14.tar.gz
read the README

Note that this program should work for most SCSI devices involving a robotic
picker and media slots.

patch kernel:
copy ch-2.2.7.diff to /usr/src/linux (ie kernel source)
patch -p1 < ch-2.2.7.diff

Compile in changer support to kernel:
make xconfig or menuconfig or just config
go to scsi section and tick changer support
put in NFS and automounter (see below) while you are at it.

If your using it as a module then add this to /etc/conf.modules:
alias char-major-86 ch
(no problems found using it as a module - recommended method of use)

run /usr/src/linux/drivers/MAKEDEV.sch (created by .diff) to create the
changer dev entries, one for the changer and one for the reader if you have
more than one reader, you will need more /dev/schx's (see
<src>/Documentation/devices.txt - again added by .diff)

Run make in the changer source directory
I had to copy scsi_ioctl.h to changer source directory and amend the Makefile.
Not sure why, so read and change the Makefile if compiler gives errors about
such a file not found (find /usr/src/linux -name <file_to_find> might be
handy) 

copy binaries to /sbin (or /usr/sbin or whatever to taste)

mover load 0
fdisk /dev/sda (create sda1)
mke2fs -b 1024 /dev/sda1 1273011
mover unload 0
mover load 1
fdisk ...
etc

"mover mv d0 d0 1" will rotate disk in drive 1
etc etc

fdisk was OK but mke2fs had problems determining the correct geometry.
the number of blocks came from dmesg report hence specifying everything
explicitly - your milage may vary.  The block size was printed on the disks as
well as from "dmesg"

The above is crying out for a quick script to shuffle through the lot.  mover
without switches will show the contents of the box.

make sure that scsi supports > 1Gb
on Adaptec 1520B - aha152x needs (in /etc/lilo.conf):
append="aha152x=0x340,10,7,1,1,0,100,1"
check source for meaning of parameters.  

I also had a weird problem where the adaptec driver appeared to caused Lilo
to forget much of the append= line - pretty esoteric but it may afflict
someone else.  I had a Frame Buffer init string in there as well and after
swapping these around (ie SCSI bit first then the video bit it worked)

The adapter BIOS had to be adjusted slightly in the CTRL-A menu on boot to
also enable extended translation.

If the geometry is wrong then mke2fs will attempt to access incorrect
addresses.  This causes the kernel to go absolutly mad, printing lots of
errors to the root console and filling up the system log.  I had to use
shift-alt-sysreq-b to re-boot after synching disks, when I got it wrong :-( 

My console was totally unusable with hundreds of messages scrolling up it.  So
if this might happen to you, make sure that the "Magic Syskey" is enabled (see
kernel docs.)  Alternatively do it in X from an xterm, that way you can kill
the job from another one ... 

Now dig out the automounter (instructions in README).  The devices are
/dev/sda1 and /dev/sdb1 (or similar) not the /dev/schx jobs.  Remember to
have automounter and nfs support in the kernel.  Attempting to cd /jukebox/0
will get the jukie to dig out the first disk and pop it into a spare drive and
even mount it.  

Not sure what the problems I had were actually caused by.  On boot the devices
were found and reported correctly but mke2fs wasn't going to play.  I even
managed to wreck one side of my first MO disk so that even fdisk refuses to
play.  You have been warned <g>  Still I do have a ridiculously large amount
of filesystem space to play with at home.  

Incidently, if you put a FAT f/s on a disk and leave it in the drive, then
Win98 can read it, if you happen to dual-boot (pah !)

Check the contents of the .diff file and the source itself - the author has
been pretty thorough with documentation.

Performance is not blistering but beats the heck out of a CDRW.

Finally, thanks to Mr Knorr for giving me an endless file system

Jon Gerdes - 17 January 2000
mailto:jon.gerdes@virgin.net

5.3 Changer Devices - Michael Heydenbluth

Hi,

I have the ANSI SCSI-II specs. Changer devices are described here.
Basically, changers are independent devices which respond to commands like:
Install disk in slot 7 in drive 2
Remove disk from drive 1 and store it in slot 13
Count all disks in the slots
and so on.
Btw. the SCSI specs make no differences between tape changers, od
jukeboxes, cd changers. These are all changer devices with the same command
set. The jukebox running under HP-UX seems to work differently from the
SCSI specs, where no LUNs for the slots/sides are defined. Three
possibilities:
1. LUNs for the disk sides are defined in SCSI-III specifications (I don't
know because I do not have them)
2. The jukebox and its driver is older than the SCSI specs, so the
manufacturer had to go its own way. This is the way my jukebox works, but
in my case the commands are similar.
3. The manufacturer choosed to ignore any specifications

Long time ago I have tried to make my jukebox work with linux. It worked
with the generic scsi driver /dev/sg*, some lines of C and a handful of
shell scripts, but I did not have the time (and knowledge) to build a real
kernel module from that.
There is still another problem: One has to write a new filesystem type for
write-once media. The ext2 filesystem can not be used because it writes
superblocks all over the disk and modifies them when data is written to the
disk. Sectors which have been written to are definitively lost. They can be
overwritten but in fact the new data is written to spare blocks and the old
data is discarded. This old data can be retrieved with special commands for
optical drives. There must be some kind of "append-only filesystem" to make
it really useful.

Greeting
Michael Heydenbluth
mh@heywei.de

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