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View Full Version : dd to rebuild boot tape on 1/4" QIC tape problems



leaknoil
November 7th, 2010, 11:57 AM
This is such a hard problem to search for on google so, I'll try here. Maybe someone will know what I am doing wrong.

I have 37 image files that made up a AT&T Unix boot tape. The original should have been a 60mb 1/4" tape. Most files are 720k but, two are 4mb. Well under the 60mb limit of a 60mb tape.

I am trying to use dd to recreate the tape. The problem is under Solaris and Linux dd to a QIC drive appears to eat up tape at a crazy rate. The 4mb file alone uses half of a 150mb tape. They will work on the AT&T box but, I can't possible fit all the files on even a 250mb length tape. I have tried all sorts of various block sizes and it doesn't seem to matter. The tape drive tears along at warp speed. I've tried a three different qic drives. a 120, a 150, and a 250. From 3 different manufacturers. All do exactly the same.

A typical attempt would be dd if=file1 of=/dev/nst0 bs=512b although I have tried block sizes up to 30k and nothing seemed to change other than what dd reported as output.

Any thoughts ?

glitch
November 7th, 2010, 12:02 PM
Are they actual dumped images? Regardless of what format they're in, you may have better luck using tar (Tape ARchive) to send the data over, though this may require some sort of conversion of the images. I've used tar with those floppy-attached QIC tapes before, so it's definitely compatible.

Dwight Elvey
November 7th, 2010, 12:04 PM
Hi
Just checking, you know the tapes are multple tracks?
Dwight

leaknoil
November 7th, 2010, 12:41 PM
Are they actual dumped images? Regardless of what format they're in, you may have better luck using tar (Tape ARchive) to send the data over, though this may require some sort of conversion of the images. I've used tar with those floppy-attached QIC tapes before, so it's definitely compatible.

They do work fine when I dd them out to the QIC drive they just take up too much tape to fit. I can boot of them annd the software does install. I just don't have enough tape to fit them all.

leaknoil
November 7th, 2010, 12:43 PM
Hi
Just checking, you know the tapes are multple tracks?
Dwight

I am not sure what you mean actually so, maybe not.

Chuck(G)
November 7th, 2010, 02:55 PM
What Dwight means is that QIC tapes are recorded in "serpentine" fashion. The drive writes a track until it hits the EOT marker, then shifts the heads and writes in the reverse direction until BOT is hit, then the process repeats. I believe that your drive uses 11 tracks, so half for 4MB, say, 10 MB per track = 110 MB, about what one would expect.

QIC drives being streamers, have only one writing speed, so they always sound as if they're gong like a bat out of Hades.

leaknoil
November 7th, 2010, 07:01 PM
What Dwight means is that QIC tapes are recorded in "serpentine" fashion. The drive writes a track until it hits the EOT marker, then shifts the heads and writes in the reverse direction until BOT is hit, then the process repeats. I believe that your drive uses 11 tracks, so half for 4MB, say, 10 MB per track = 110 MB, about what one would expect.

QIC drives being streamers, have only one writing speed, so they always sound as if they're gong like a bat out of Hades.


I get it now. I've been using 1/4's drives forever and never knew they reversed direction. In my own defense I was a recording engineer for a long time and just assume there is a multitrack record head where there are multiple tracks.

I can't believe how much time I have wasted on this non-problem. It all started with a write error that must have been right at the end of the tape just by chance. Then I watched tapes hit the end and assumed the worst. Doh

http://i963.photobucket.com/albums/ae112/Selphos/Facepalm/picard-no-facepalm.jpg

dbeaufor
February 15th, 2011, 11:52 AM
The AT&T box , is it a D5 use from telco compagny ?

Thanks



This is such a hard problem to search for on google so, I'll try here. Maybe someone will know what I am doing wrong.

I have 37 image files that made up a AT&T Unix boot tape. The original should have been a 60mb 1/4" tape. Most files are 720k but, two are 4mb. Well under the 60mb limit of a 60mb tape.

I am trying to use dd to recreate the tape. The problem is under Solaris and Linux dd to a QIC drive appears to eat up tape at a crazy rate. The 4mb file alone uses half of a 150mb tape. They will work on the AT&T box but, I can't possible fit all the files on even a 250mb length tape. I have tried all sorts of various block sizes and it doesn't seem to matter. The tape drive tears along at warp speed. I've tried a three different qic drives. a 120, a 150, and a 250. From 3 different manufacturers. All do exactly the same.

A typical attempt would be dd if=file1 of=/dev/nst0 bs=512b although I have tried block sizes up to 30k and nothing seemed to change other than what dd reported as output.

Any thoughts ?

pitlog
March 10th, 2011, 05:07 PM
The AT&T box , is it a D5 use from telco compagny ?

Thanks

Actually, I think it was a 3B2/600G.