remote tar backup - I/O error

[Fredric Persson]

What is the best way to backup remotely using the tar command (we have Omniback and Legato)?

I have tried this:

On source system (Sun Solaris 7)
tar cvfBh - | ssh root@ dd of=/dev/rmt/2m

F.Y.I.
tar options, B - Block, force tar to perform multiple reads(if necessary) to read exactly enough bytes to fill a block.

tar options, h - Follow symbolic links

ssh - secure shell (not necassary, but we have a high security standard)

Remote server is a HP, K570 with a Quantum 7000 DLT (4 drives).

I have mounted the tape with the mc command and it is about 20GB data.

It worked fine, but after about 2h I got I/O error.

Am I doing the right thing?

Thanks!

//Fredric

[harry d brown jr]

You could try GNU's tar, if you want a tar tape, and it handles large files, but you will need GNU's tar to retract if you move the tape to another system:

http://hpux.connect.org.uk/hppd/hpux/Gnu/tar-1.13.22/


live free or die
harry

[Sanjay_6]

Hi Fredric,

Take a look at the thread below,

http://us-support.external.hp.com/cki/bin/doc.pl/sid=b4b285091b7cfbd55c/screen=ckiDisplayDocument?docId=200000055821055

http://us-support.external.hp.com/cki/bin/doc.pl/sid=b4b285091b7cfbd55c/screen=ckiDisplayDocument?docId=200000024669442

An IO error can also be due to an error on the tape media.

Hope this helps.

thanks

[Frank Slootweg · Accepted solution]

I do not know what block size Sun Solaris 7 tar uses, so I will assume the default 10KB.

The general problem is that a 'remote pipe' does not guarantee a certain blocksize out of the pipe. I.e. if you write 5 records of 10KB, you will get 50KB out of the remote pipe, but not neccessarily in 5 records of 10KB.

To solve this problem, use dd(1) commands around the remote pipe (You used one dd(1) command, but you should use two and you should specify the right block size). I have left off the Solaris option B and assume 10KB (20 blocks) records:

tar cvfh - | dd bs=10k | ssh root@ dd bs=10k of=/dev/rmt/2m

To check the block size which Solaris' tar uses, you can use:

tar cvfh - | dd bs=64k of=/tmp/record count=1 ; ll /tmp/record

If it is other than 10KB, then use tar options until it is 10KB. Don't use anything smaller, because it gives a bad performance on a DLT. If you use something bigger, then note it down, because it is non-standard.

Out of interest, why are you using tar when you have OmniBack and Legato?

[Fredric Persson]

I??m going to send the DLT tape to another site, where they don??t have Legato/Omniback (Netbackup).