vxdump and Ultrium performace

[Mattias Johnsson]

Can someone please explain how to tune the performance of vxdump -> Ultrium. We are writing ~110Gb of uncompressed data (~700000 files) to a Ultrium 100/200 tape with vxdump and it takes over 9 hours to write 20%! That just can not be correct.
The options we use are
-0f /dev/rmt/c6t1d0BESTn /archives

Backing up the same filesystem with
find . -print | ftio -oacpv -B 32k
only takes 4 1/2 hours!
I always thought that vxdump was far superior to ftio?

Any help appreciated
Cheers
/Matt

[Leif Halvarsson_2]

Hi,

I am not sure vfxdump is far superior to ftio, ftio is perhaps old but it is rather fast.
But also 110 GB in 4.5 hours seems to much when using a Ultrium drive. What kind of hardware (disk system, server etc.) do you use ?

[Mattias Johnsson]

Hello,

The server is a superdome 32000
w 12 cpu + 24Gb running against a hitachi SAN via fiberchannel.

We do all our database backups using ftio, so if you have any tuning advice for ftio as well I would be really very grateful!

Cheers
/Matt

[Leif Halvarsson_2]

Hi,
I made a performance test (ftio, vxdump and OmniBack) on one of our systems (A400, SAN attached disk and Ultriom drive).

With ftio and vxdump I got almost identical performance (1GB/min) with OmniBack slightly better (1.2GB/min). The data I used for testing give a rather poor compression ratio < 2-1. With 2-1 ratio data it should not be impossible to get the full Ultrium performance (1.8GB/min).
Of courese there is differences with the number of files and average filesizes (compared to yours) but this can't be the only reason.

There must be some performance bottlenecks in yous system, I would suspect the disk system.

[Mattias Johnsson]

Aftere some testing I have got the backup time down to just over 3 hours in total! Just by using the
vxdump -B 200G -0f
options!
This makes me wonder if the ftio options we are using for normal database backups are optimal....
ftio -oacpv -B 32k

[Massimo Bianchi]

Hi,
I think one of the problem could be the HUGE number of different files.
When you pad it with ftio performances gets better.

With an ultrium i would use a -B 256K (this is the setting we use on OB).

HTH,
Massimo

[Leif Halvarsson_2]

Hi,
Ther was an whitepaper at HP Storage "How to get best performance of Ultrium drives" with performance figures for different blocksize settings but I can't find it, perhaps is is not longer avilable. 32k should be enough, perhaps you get slightly better performance with 64k, but increasing above this value will give no improvement.