Fbackup and DLT Autoloaders

[Jenifer Martins]

I recently installed multiple patches to get fbackup to work with my new DLT Autoloader. I read that I need to use "tcio" with fbackup to "buffer up" when data is going to the device. I just want to know the correct commands to backup to using fbackup to my new autoloader. Does anyone know?

Secondly, I am having difficulty backing up more then one "graph" to the same DLT. Usually, I use device /dev/rmt/1m for the first graph, then /dev/rmt/1mn for the following. However, when I tested frecover, it only sees the last graph I backedup. The "mt" command to rewind isn't working either. Any suggestions?

Does anyone have any good HPUX books that they recommend? Something with details of backuping using fbackup?

[Bill Hassell]

Not sure what document you are reading but there are several errors. First, tcio has been obsolete for many, many years. It was never designed for any modern tape drive, definitely not for DLT's. It exists to support the long-obsolete CS-80 tape cartridges that had random access, similar to disks with a whopping 67 to 132 megs maximum per tape.

fbackup, like commercial quality backup programs, does not allow appending multiple backups on a single tape. This is due to the design of these tools which always puts a complete directory listing at the beginning of every tape. Concatenating multiple backups is a very common way to destroy good data or to lose it. If you can afford a DLT drive, your data is obviously very valuable and needs a reliable backup strategy.

If a second tape is required, there are two choices: Use 2 (or more) tape drives and specify all of them with multiple -f options, or write a chgvol script which calls the mc command to change the tapes.

The mt command works fine but be sure to read the man page about the (bizarre) behavior os AT&T device files versus Berkely style. You can certainly use mt to space forward, but fbackup ALWAYS rewinds the tape before writing due to the design mentioned before. The reason that you saw only the last backup was that fbackup overwrote the previous backup. fbackup incorporates some rudimentary checking of the tape label to prevent overlaying the first tape with data destined for an additional tape.

fbackup works fine for DLT's with the latest patches. However, with all modern tape drives (DDS, Exabyte and DLT), you MUST use a configuration file to specify reasonable record sizes, reader programs, checkpoint and fast search frequencies. Here is a sample config file:

blocksperrecord 128
records 32
checkpointfreq 1024
readerprocesses 6
maxretries 10
retrylimit 5000000
maxvoluses 200
filesperfsm 2000
chgvol $HOME/chgvol.sh
error $HOME/error.log

The last two files should be adjusted to fit your system.

As far as documents, start by bookmarking: docs.hp.com and search for the word: fbackup