Here is the procedure for all fbackup multi-tape sets: Always put the *LAST* tape in first. Here's the reason: fbackup has no way to tell how much data will fit on each tape. Compression and bad spots on the tapes make this impossible to predict. Once fbackup reaches the end of the first tape, it requests the next tape. The first thing written on each tape is the fbackup header (which includes the tape number) plus a complete index of all files and directories that will be saved and a marker as to the first file on this new tape.
So tape #2 knows exactly what's on tape #1, tape #3 knows about tape #1 and #2, and so on. Only tape #7 knows where all files are located. Since the index can be read in just a few seconds, you can reach any file or directory in just a few minutes with just two tape changes. This technique is very common with commercial backup programs. Note that high speed search is standard with fbackup/frecover but is disabled when the destination is not a 'real' DDS or DLT tape (ie, a network connection)
However, these two messages indicate a very serious situation:
> I INSERT THE 2ND TAPE
> frecover(5423): incorrect volume mounted;
> frecover(5424): expected volume 2, and got 1
This means that what you thought was tape #2 is the original tape.
> I INSERT THE 3RD TAPE
> frecover(2105): did not find expected file marker
> frecover(5409): unable to read volume header
> frecover(5418): not an fbackup volume; unable to read volume header
This means that the 3rd tape has nothing to do with fbackup. It is a tar or cpio tape or somehow got overwritten or mixed up in your backup set. Based on this and the previous tape, you don't have a useful backup of your data at all! This illustrates the difficulties in managing multi-tape backups. Very careful marking and handling of the tapes is critical. fbackup will record a volume header on each tape. Use:
frecover -V - -f /dev/rmt/
on each tape to read the header. If you are not using a config file with your fbackup command (-c option), your tapes are not being recorded efficiently at all and you may be able to reduce the recording time for each tape by 30-60%, perhaps reducing the tape count from 7 to only 4-6 tapes. Put this into a file in /etc/fbackup.conf:
blocksperrecord 512
records 64
checkpointfreq 1024
readerprocesses 6
maxretries 5
retrylimit 5000000
maxvoluses 200
filesperfsm 2000
Then run fbackup with the required options plus: -c /etc/fbackup.conf
The reason that this helps is that the defaults are designed for reel-to-reel tape drives, not DDS or DLT/LTO.
Bill Hassell, sysadmin
