anthony@cit-vax.Caltech.Edu (Lawrence Anthony) (01/10/90)
we recently acquired a 1.3GB DAT tape backup unit from tristar technology for our decstation 3100 running ultrix 3.1/uws 2.1. the drive unit is made by wangtek and uses the dec-approved DDS data format. it is presently being used as a plug-and-play device and emulates an exabyte, i.e. scsi_devtab.devtype = TZxx in /sys/data/scsi_data.c. so far i have been able to use dump/restore and tar quite successfully except in the following cases: 1. using "tar c" to create a tape archive on the DAT unit works fine. however, i cannot seem to add files to the archive using the "tar r" command, at least not reliably. i frequently (though not always) obtain the following error message during the read and/or write stage: tar: Directory checksum error, possible file name: this is followed by some gibberish that does not look like a file name but more like part of a file on the tape. this error is reproducible with different tapes with the error seeming to occur in exactly the same position on the tape (judging by the gibberish that accompanies the checksum error message. is this a known bug/limitation in using tar with the "r" option under ultrix? or is this related to the oft-mentioned even- versus odd-byte disconnect problem with exabytes. 2. the command "dd if=/dev/rmt0h of=/dev/null" gives the following error message when used on recently written dump tapes: read: No such device or address 12+0 records in 12+0 records out using /dev/nrmt0h instead of /dev/rmt0h gave the identical error message. this was done with a tape onto which i had just written a dump of my root (/) and /usr filesystems. i know that the files were written correctly as i have been able to restore a random sampling of the files on the tape using the restore command. i like to use this command to verify that there were no errors on my dump tape. this procedure works properly when using dump/restore with tk50 tapes. similar error messages were obtained with a recently written tar tape as well as with files written using the command "cp filename /dev/rmt0h". i can however read back files from the tape using the "dd" command if the files were copied to the tape using the "dd" command in the first place. 3. the command "mt status" under csh gave the following error message: DDS DAT tape drive, residual=0 Segmentation fault issuing the same command under the Bourne shell (sh) gave a slightly different error message: DDS DAT tape drive, residual=0 Memory fault the above messages were obtained with a tape loaded into the DAT unit. in contrast, most of the other mt commands that i have tried, such as "mt rewind" and "mt -f /dev/nrmt0h fsf 1" seem to work okay. using "mt offline" even causes the tape to be rewound and ejected. 4. does anybody have any suggestions for using the DAT unit to back up VMS systems over ethernet (either Decnet or TCP/IP) and to back up Macintoshes over ethertalk/localtalk/ethernet? (we have an appletalk- to-ethernet bridge from Cayman Systems.) specifically i would like recommendations for software products and vendors. would the vms-ultrix connection software do the job for vms? 5. i don't suppose dec will be releasing ultrix 3.2/uws 3.2 on DAT tape? any explanations/solutions would be greatly apprecitated. please direct followups to comp.unix.ultrix. (i had mistakenly requested that followups go to comp.sys.ultrix in an earlier cancelled posting.) thanks in advance. lawrence anthony e-mail: anthony@csvax.caltech.edu phone: (818) 356-4474 FAX: (818) 795-1547