[Dvdrtools-users] Safecom External Firewire/USB 2.0 Housing and an LG GSA-4167B

[Alec Edworthy]

Hi,

I've been advised to post a message to the list by a friend. This
problem doesn't directly relate to any specific DVD software but
it is sort of DVD drive related.

Recently I bought a SafeCom external USB 2.0 and Firewire 1394a
5.25-inch caddy to house an LG GSA-4167B DVD Multi Writer. I've
used my laptop with firewire devices before but only for short
periods of time, this is the first firewire device I've actually
owned. My laptop is a Dell Inspiron 8200 with a Pentium 4 1.6GHz
processor, 384Mb RAM, on-board USB 1.1 and Firewire, DVD/CD
reader and an 80Gb HDD (60Gb for Fedora Core 3, 20Gb for Windows
XP Professional SP2).

When I first plugged it in I only had access to CDRs and all
seemed fairly well with it. I was able to write the CDs and read
them back in the internal CD drive. Not long after that I got
hold of some RiDisc DVD-Rs (Media Code: TTG02) but when I tried
writing to them I found that I got a lot of errors in
/var/log/messages like,

Jan  9 13:51:18 euclid kernel: ieee1394: sbp2: aborting sbp2 command
Jan  9 13:51:18 euclid kernel: Test Unit Ready 00 00 00 00 00

along with some errors like this,

Jan  9 10:49:55 euclid kernel: Device sr0 not ready.

cdrecord was saying things like this,

cdrecord: Input/output error. write_g1: scsi sendcmd: no error 
CDB:  2A 00 00 00 00 00 00 00 1F 00
status: 0x2 (CHECK CONDITION)
Sense Bytes: 70 00 05 00 00 00 00 0A 00 00 00 00 21 02 00 00
Sense Key: 0x5 Illegal Request, Segment 0
Sense Code: 0x21 Qual 0x02 (invalid address for write) Fru 0x0
Sense flags: Blk 0 (not valid) 
resid: 63488
cmd finished after 119.085s timeout 200s

I tried writing some DVD-RWs and they seemed to work but I still
got a lot of errors (in /var/log/messages). When I tried
simulating the writing of the DVD-Rs (so not to waste discs, as I
had been trying in Linux) in Windows XP they seemed to work which
puzzled me a little. I also discovered that I wasn't able to read
CDs or DVDs in Linux using the external drive. At this stage I
decided that I needed to look into where the problem was. I got a
standard IDE hard disk drive and tried that in the external
housing first. I was able to connect to it and do basic stuff
like ls the drive but when I tried probing deeper into the
directory structure I got a lot of errors from the sbp2 module
again. This suggested to me that it wasn't the DVD drive which
was at fault, rather it was more likely that Linux had some
issues with the firewire side of things. I tried switching to USB
1.1 and found that it worked, albeit rather slowly. Putting a
CD-ROM drive in with USB 1.1 also worked. I tried putting the DVD
drive back in and found that I was able to write DVD-RWs with the
unit plugged into the USB interface.

After a fair bit of Googling and experimentation I was able to
get the external housing working over firewire by using the
serialize_io option[1] to the sbp2 module which is commented as,

  Turn on serialization for debugging, for some buggy SBP-2
  devices (or bug in sbp2?), or to work around new problems in
  new sbp2 revisions

Buggy devices - that'll be mine then! After doing that I was able
to read CDs fine in the CD-ROM drive I had in it at this stage.
Swapping that for the DVD writer drive produced similar reading
results. Next on my list was to try burning a disc. I grabbed my
DVD-RW disc and had a go and was impressed when it actually
worked. I then tried a DVD-R disc and it failed. This was not
good but after a little more Googling I came across the comment
that TTG02 media is not liked by LG drives[2]. I grabbed a Sony
DVD-R disc and that worked fine.

One unfortunate side effect of using the serialize_io option
seems to be a massive reduction in throughput. With the hard
drive I was trying (a 60Gb Seagate Barracuda, formatted as ext3)
I was getting around 10Mb/sec which equates to around 83Mbps -
nowhere near the 400Mbps firewire 400 can get or the 200Mbps I
have had in the past with a Maxtor 250Gb OneTouch external hard
drive (formatted as NTFS iirc). With the DVD drive in I see
around 7Mb/sec which is good enough for CD burning up to around
50x according to cdrecord (I don't think I actually get this
speed though) or DVD burning up to around 6x.

I've just ordered some Verbatim (Taiyo Yuden) DVD-Rs (Media Code:
TYG02) and hopefully once they arrive I should be able to burn
DVD-Rs under both Windows and Linux. Saying that though I haven't
really had that much cause to write CDs or DVDs recently so I
don't know when I'll get around to having another go.

As an aside, it seems that I cannot simulate writing to DVD-Rs in
Linux using cdrecord. I had thought that the lack of simulation
burning was limited to DVD+R(W)s but perhaps I am mistaken.
Should simulation work for DVD-R(W)s?

Well, hopefully this posting might be of use to someone out there
at some point.

Alec

1. http://www.linux1394.org/sbp2.php
2. http://club.cdfreaks.com/showpost.php?p=1223038&postcount=5

-- 
Alec Edworthy
address@hidden