fbackup in two different tapes

[GSB_3]

Hi,

I have two tapes 72 GB (HP DAT72) and 40GB (HP DDS-4).
I have to take backup of 96 GB data and If I start the backup using fbackup with first tape 72GB (HP DAT72).Can I inset the second tape 40GB (HP DDS-4) once it asks for the second tape.

Are both compatible?

thanks

[Robert-Jan Goossens]

Hi,

Not within one session, you can however use two HP DAT72 tapes, if the first one is full fbackup will ask for a new tape.

Regards,
Robert-Jan

[GSB_3]

thanks for the response.

You mean to say that once it asks for the second tape I can't use the 40GB tape.?

waiting for ur reply.

Thanks

[V. Nyga]

Hi,

as said - if you run fbackup interactively, you're asked to tell the new device file, when the first tape is full.
Also I think it would work to give the second tape device, there's no need to do so, and I think it would confuse.
You only have to change the tape and give the same device file.
But this will not work for an automated backup (with cron).
What do you mean with compatible?
The DAT72 will also read a DAT40 tape, but not versa.
http://www.hp.com/products1/storage/pdfs/media/compatibility.pdf

Please also note, that a DAT 40 has a native capacity of 20 GB and a DAT72 of 36 GB.
Only if your files can be compressed with a 2:1 ratio you can use the highest capacity.

HTH
Volkmar

[whiteknight]

GSB,

It is compatible, you can use.

Check this out.
http://www.hptapecompat.com/




WK

[V. Nyga]

Hi again,

sorry, maybe it only works if you use 'tar' to store files at a tape.
If you use 'SAM' for example to backup files (it also uses fbackup) you have to choose the backup device at the beginning, so no chance to change it.

V.

[V. Nyga]

Hi again,

see 'man fbackup' - you have to tell the device at the beginning.

So if you want to change the device file you could use tar - but fbackup is much better for recovery!

V.

[Bill Hassell]

This is not a problem at all. The fbackup man page is helpful:

-f device [ -f device ] ...

"If more than one output file is specified, fbackup uses each one successively and then repeats in a cyclical pattern. "

So your fbackup command will something like this:

fbackup -c configFile -i / -v -f /dev/rmt/1m -f /dev/rmt/2m

(you supply the correct devicefile names for the tapes). When fbackup reaches the end of the first tape, it will automatically use the next tape, and so on per the man page. fbackup does not care at all about mixing the type of tape drives. Always use a config file for maximum performance:

cat fbackup.config
blocksperrecord 4096
records 64
checkpointfreq 4096
readerprocesses 6
maxretries 5
retrylimit 5000000
maxvoluses 200
filesperfsm 2000

[Bill Hassell]

Note: automatic tape switching only works when you have multiple drives. You can manually swap tapes when requested. The media can be different as long as the drive itself can use it. A DAT72 drive will accept DDS5 (DAT72) and DDS4 tapes. Note that the media names (DAT72 and DAT40) are twice the size of the tape's capacity. Marketing assumes that your data files can be compressed by at least 2:1 but this is nothing but a guess. So you can safely assume that your data is not compressible so you'll get 36GB on the DAT72 tape and 20Gb on the DDS4 tape, for a total of 56GB, perhaps a bit more.

To safely backup 96GB of data, you'll need three DAT72 tapes. Naturally, if this data is important and changing a lot, you'll need several boxes of DAT72 tapes so you can keep older backups for a while.