problem with backup using tar and DLT tape drive

[Diane Cardone]

I am currently running HPUX 10.2 and have been running backup scripts using the tar command. I am backing up a little over 40 gig of data to a DLT 8000 tape drive. The backup times were running at approximately 31/2 to 4 hours. Suddenly the backup times almost doubled and I can't figure out why. We even had HP replace the drive thinking there was something wrong with it. Can anyone give me an idea of why the backup times increased so much or how I might be ablr to diagnose what the problem might be.

Any help would be greatly appreciated.
Thanks.
DKM

[Michael Tully]

I can only think that something has changed on your system..... What changes have any been made just around the time of the problem starting?

Have you attempted to run a different type of backup instead of tar to get a comparision? Try using 'fbackup'

You could try to use the mstm/xstm tools and diagnose your SCSI card that your tape drive attaches to.

[Diane Cardone]

I would assume (maybe stupid on my part) that if HP hardware support changed the tape drive they would didn't find any other problems with the hardware (cards, etc).

[Michael Tully]

One thing to remember as a sys admin is to never assume.... Was that test I mentioned ran?

More thoughts:

Tape drive firmware level V59 (although there is a later one out that I've heard is not great)
Greater space that needs to be backed up? i.e. Additional filesystems that have been created.

No other hardware was added to the same SCSI chain, i.e. an additional tape drive for example.

Michael

[Diane Cardone]

I have never used fbackup so I am not that familiar with it. I'm thinking this could be a block size problem, but I'm not sure how to change it on HP (I'm more experienced with AIX than HP). The diagnostic commands you suggested, can I run them while others are using the system? What should I be looking for?

DKM

[Michael Tully]

Hi,

Yes you can, there is no problem running the test.

To use 'fbackup' you could try this.

Add each of your filesystems to a file called /tmp/graph
in this format.

i /
i /stand

etc etc for each one that want

Save the file. and run this:

# /usr/sbin/fbackup -g /tmp/graph -f /dev/rmt/0m
(substitute your tape drive device)

This will backup your entire system. See how long it takes compared to your backup. Have a look at the man page for fbackup for more information.

-g creates the archive from a given file.
The 'i' in the file means include.
-f means the device to be used.

HTH
Michael

[A. Clay Stephenson]

One thing that could cause a 2x loss of speed would be if the drive is not going into compression mode. You should be able to note that by observing the front panel LED's.

I assume that the data volume is the same. Your filesystems could have become severely fragmented.

To be honest, tar (being single-threaded) has a tough time keeping a hi-speed tape drive fed.
That is one of the main advantages of fbackup. It can (and should) have multiple reader processes to better feed your drive and keep it streaming. If you notice that your drive is constantly running a bit; stopping and running again, it's started for data.