Tape will be full?

[S.Keung]

Everyday, I change the slot and use "tar" command to backup data into tape. i.e. Slot 1 for Monday, Slot 2 for Tuesday, etc.

Will the autoloader erase the data when i change the slot? If not, the tape will be full after few weeks.

[melvyn burnard · Accepted solution]

Provided you are not appending to the tar archive (using the -r option), then tar will start from the beginning of the tape and overwrite the data that was on it.

[John Carr_2]

this will reuse the tape each time unless you tell tar to append :-) John.

[S.Keung]

Yes, i use "tar cf /dev/rmt/0m ".
So, the changing slot operation will not erase any data.
Thanks!!!

[Leif Halvarsson_2]

Hi,
If you use a autoloader, the tape is rewound when you change slot and when the tape is loaded next time, writing is done from the beginning of media (tape is overwritten).

But, why do you use tar for backup, fbackup (standasd HP-UX utility) is a better alternative. Or, even better, Data Protector.

[Michael Duthie]

If your loading the tape and then using "cf" you will write at the start of the tape and overwrite whats on it.

[S.Keung]

The tape is automatically rewound when i change slot. How to disable auto-rewind when i change the slot?

"tar" / "fbackup" / "Omniback" - Which is the best backup tool? Can you simply explain?
Thanks!!!

[Victor BERRIDGE]

If you want not rewind, you will have to choose a no rewind device e.g. for /dev/rmt/0m that would be /dev/rmt/0mn
The n at the end of the devices namemeans no rewind...

Good luck
Victor

[Michael Duthie]

You can't disable rewind, you would need to load the tape then use append, -r, as stated above.

Fbackup is good (far more flexible than tar) and free but you need to move the tape manually with the "mc" command.

Omniback is better but you have to pay for it. Omniback is a worth looking at if you have 2 or more systems and want to utilise your tape libary to back up centrally.

[Michael Duthie]

Victor is correct for a tape already loaded but if you load a tape it rewinds automatically.

[Mark Grant]

If you have the set_san_safe kernel parameter set you have no choice but to use the no-rewind device.

Also, if you don't use the no-rewind device and you don't manually rewind it yourself when you change the slots, your tapes will fill up because your tar backups won't overwrite the previous one. You might not be even able to restore them.

You backup software depends on what you are doing. If you can fit all your backups on one tape, I would suggest you use "tar" or "fbackup" as these come with the machine and do a reasonable job though fbackup is preferred.

If you have a larger environment, I would have to suggest Omniback/Data Protector, not becuase it's the best (it is very good though) but because you do not need to pay for a license for the clients.

[Bruno Ganino]

I use fbackup command...
this is explanation
http://www.freelab.net/unix/hp-ux/chap07_backup.html
HTH
Bruno

[Leif Halvarsson_2]

Hi,
When unloading a tape from a drive (in your case the internal drive) the tape is always rewound. If you want to append data to the media (not overwrite) you have to use the mt command for forwarding the tape (see the man page for mt).

fbackup is a standard HP-UX backup utility and is free. It can be described as a low-end backup program. For details, just do a "man fbackup".

Data Protector is HPs hig-end backup program, it is not free but you can download a evolution copy at:
http://www.openview.hp.com/products/datapro/spec_0001.html

[Michael Schulte zur Sur]

Hi,

man tar reveals
r Add the named file to the end of the archive. The same
blocking factor used to create the archive must be used to
append to it. This option cannot be used if the archive is a
tape.

Omniback allows you to choose to select how long a tape must keep its data and so, how long it appends.

greetings,

Michael

[James Lynch]

If you are really set on using the tar command, then you could use the mt command to reposition the tape to end of the previous tar backup. You would have to either keep track of this info on a per tape basis, or you would have to dynamically figure this out each time you load the tape and want to append to it.

The steps for using mt are as follows:
load the tape into /dev/rmt/0m
mt -f /dev/rmt/0mn fsf 1
repeat the above mt step until you get to the end of all of the tar archives on the tape.
tar -cf /dev/rmt/0mn /dir

Beware, unless you are maintaining an index for the tar archives and where they are located, restoring an individual file will be very difficult. Also using this method is very slow, and adds quite a bit of overhead. You would be much better using a true backup program like OmniBackII.

JL