paolucci@chaos.ame.nd.edu (Dr. Samuel Paolucci) (05/24/91)
I have a problem that I hope someone can help me with. I have a QIC tape with important information in it. This tape was write protected. I used it last to get stuff from it about a month ago. The info is saved in it in tar format. A couple of days ago I tried to get stuff from the tape and very quickly tar stops without retreiving anything. If I persist by using mt by skipping files, it tells me that I've reached the end of the tape. I've also tried using dd in reading the tape, but I've been unsuccessful. It seems that somehow an end-of-tape mark is read near the beginning of the tape and all the unix utilities (tar, mt, and dd) refuse to go past it. The only exception is if I retension the tape in which case it goes from beginning to end. In all the above attempts I have tried using the utilities repeatedly using the no-rewind device (i.e. /dev/nrst0). I suspect that the difficulty I'm having in trying to move through the tape is due to the device driver that all these utilities make use of. Can somebody give me any suggestion, or have any utility that will allow me to recover the info I have on tape. I will be eternally grateful. Please only reply by E-mail since I don't read this newsgroup often enough. -+= SAM =+-
wolfgang@wsrcc.com (Wolfgang S. Rupprecht) (06/05/91)
paolucci@chaos.ame.nd.edu (Dr. Samuel Paolucci) writes: >I have a QIC tape with important information in it. This tape was >write protected. [...] A couple of days ago I tried to get stuff >from the tape and very quickly tar stops without retreiving anything. >If I persist by using mt by skipping files, it tells me that I've >reached the end of the tape. Sun's tape SCSI driver is pretty eager to rewind and call the quits as soon as it hits a bad block. I tried to read a 5 year old QIC tape with a bad oxide spot after a few megabytes. The Archive Viper would read along until it hit the bad block. The tape drive would try to re-read the block a few times and give up with an error. At this point the Sun device driver would basically over-react and set the tape-block number to unknown and force a rewind on the next tape open. There was no way that I could think of to skip over this bad section and continue reading the next good block. What I did is find another company's computer and try to read the tape on that. I eventually read my tape of on a BULL DPX-2 (68030 SysV Unix box). I just did several dd's and got two multi-megabyte files and several zero-length files. I spliced the two real files together with 3 blocks worth of NULLs and fed the resulting file to tar. I got all the date back except for those 3 trashed blocks. Too bad one can't use a Sun to do this and has to use some other company's computers. -wolfgang -- Wolfgang Rupprecht wolfgang@wsrcc.com (or) uunet!wsrcc!wolfgang Snail Mail Address: Box 6524, Alexandria, VA 22306-0524