Slow Restore from an Ultrium Tape

[Bamidele Jolayemi]

We do system backup of our enterprise server on to 200G Ultrium tape. The backup usually lasts about 2 hours, but a restore of same backup set done in 2 hours lasted several hours running into 18 - 20 hours.

What could be responsible for this?

One observation is a directory with 21000 files took about 10 hours in the course of the restore.

Any help will be appreciated.

Thanks.

[Stefan Farrelly]

Firstly backup devices are designed to backup fast, restores always take longer than a backup.

Are you using fbackup ? you didnt say which backup tool you are using. If it is fbackup there are some configuration options you can set to make restores faster (more checkpoints etc.). Here is the one we use which is a nice balance between backup speed and decent recovery speed;

blocksperrecord 128
records 32
checkpointfreq 256
readerprocesses 4
maxretries 1
retrylimit 0
maxvoluses 1000

(/var/adm/fbackupfiles/config)

[Robert-Jan Goossens]

Hi,

check this doc,

http://www.hp.com/products1/storage/products/tapebackup/ultrium_tapedrives/ultrium230/infolibrary/whitepapers/ultperfpress.pdf

I don/t know if you are using parallelism for faster backups, disadvantage can be that the restore is slow.

Hope this helps,
Robert-Jan

[Jean-Luc Oudart]

Check this thread.
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=45872

We would not use fbackup for full server backup. For that, we use OBII/DP and there is not much differences between backup time and restore time.

Regards,
Jean-Luc

[Elmar P. Kolkman]

Possible problems:
- Creation of files takes time. Especially on vxfs filesystems. So if you have lots of small files, they are slow to recover
- having verbosely output what you restore to a slow terminal session, for instance a 9600 baud console, can slow down a restore really good ;-(

These two are reasons I've seen, next to the other reasons the others gave, for slow restores.