Whats happens if I use a no rewind device for a single fbackup?

[N Ward]

Hi, I have created some tapes via fbackup using a no rewind device (I wasn't aware that it shouldn't be used, there is no explanation why either??). Will these tapes be usable? They have multiple file systems on them.

[ani007]

Hi,
fbackup always rewinds the tape before the backup starts and I think, when it finishes.
better just using /dev/rmt/0m.
If you are trying to put more than 1 fbackup on a tape,You will not be able to do it.Are you able to do the listing (frecover -f /dev/rmt/0m -x -N -v [listing].I think you should be able to continue that device and frecover should work just fine.
regards,
Ani

[N Ward]

Hi thanks for your reply, why is it a problem if fbackup always rewinds the tape at the start and end? If there is one backup on the tape that isn't a problem is it if it does that?

I haven't tried frecover the tapes have gone to a third party, but I think they are having problems..

Is it because if you choose a no rewind device fbackup WONT be able to rewind at the start and end? Is that what the problem is?

[ani007]

Suppose you want multiple filesystems with fbackup.
1.Best way to do is graph file so in future you can update it easily.

2.You can also use the fbackup manually and include those filesystems - using a no rewind device.

fbackup -i /home -f /dev/rmt/0mn (n is for no rewind)
fbackup -i /var -f /dev/rmt/0m (no need to rewind if this is all you are putting on the tape)

Normally /dev/rmt/1mn would be the no rewind device - typically for large tapes and small backups you'd use the no rewind so that the next time you put in the tape it would add another backup at the point the first one had left off rather than continually overwriting the first backup.

[N Ward]

Hi thanks for your reply...

I'm not entirely sure I understand what you are saying :o)

The fbackup we have done for example is this:

fbackup -0 -i /u01 -i /u02 -i /u03 -f /dev/rmt/c14t33d0BESTnb

would this be ok? its a one off backup.

[ani007]

yes it is ok.you can use -I option which will create a index file (from that file you can check whick files are backedup)
ex.
fbackup - -vf /dev/rmt/cXtXdXBESTn -i /-I /home/index1 (index)

[ani007 · Accepted solution]

please dont forget to assign points :)

[N Ward]

Many thanks for your help.

[Dennis Handly]

>I have created some tapes via fbackup using a no rewind device

I thought fbackup explicitly checks for no rewind and would abort? Under WARNINGS it says:
fbackup should not be used with no-rewind devices
(Perhaps I'm confusing this with ignite.)

To validate your tapes, use frecover as mentioned by ani007.

[N Ward]

It certainly didn't complain when I ran some tests with the no rewind device first. It would be great if there was an explanation with the written warning that told you why the no rewind device shouldn't be used.

[Dennis Handly]

>It would be great if there was an explanation with the written warning that told you why the no rewind device shouldn't be used.

Probably the obvious, if you think you can append backups to the tape, you would get a big surprise if they were overwritten.

[grahamswilson]

I'm also not sure why the documentation says what it does...but what I can tell you for sure is that there is NO way to put multiple, seperate fbackup sessions onto the same tape. Whatever device you use, it will always rewind, and by design will therefore always OVERWRITE whatever is on the tape...there is no WAY to append one fbackup to another...

(It's something to do with the clever way fbackup stores its index - which has to be at the beginning of the tape I believe.)

This is a shame as fbackup is pretty good...and it still sounds like HP are possibly removing it at some point too...

[N Ward]

Yes it does seem strange.. The tapes are being read ok too, which is good news.

[Bill Hassell]

> ...it does seem strange..

Not at all. fbackup, unlike tar or cpio, places a complete directory at the front of the tape. That's why you can list the complete contents of a tape (or even a multi-tape backup) in just a few seconds, whereas tar or cpio must read the entire tape to produce a contents listing. That's why fbackup doesn't care about the device file's rewind action. The tape will always be rewound by the program (which is more predictable than a driver option). If fbackup doesn't like the device file, it will tell you. The device file will not affect the backup.