|
Re: [Veritas-bu] Max Fragment Size for Disk and LTO4 Based Storage Units
2008-02-01 14:10:19
On Feb 1, 2008 9:11 AM, Bryan Bahnmiller <bryan.bahnmiller AT managedmail DOT com> wrote:
I did a lot of testing at one point trying to tune NetBackup for
DSSU's, LTO2 and LTO3.
I found that 1024 MB fragments would never even spin up the LTO3
drive. It would basically start to speed up, then it would slow down
because it had to position for the next fragment. Total time - 6 seconds!
After much experimentation, I found that 6GB fragments worked best
for LTO2 and 10GB fragments best for LTO3. (Local FC attached high speed
disk to FC attached tape drives.) LTO4's could probably even use larger
fragments, I never tested them.
Hi Bryan,
How did you determine that 10GB fragments were optimum? Out of curiosity, why not 20? We picked 20 as a rough number and not because of any serious benchmarking. Did you just discover that it wouldn't write any faster than if you picked 10 so you stuck with that?
What sort of destaging performance are you getting? We've found, in general, destaging performance is pretty poor but we've never been able to identify the bottlenecks and all the help we've gotten from NetBackup support and engineering hasn't made it any better. We can write fast but we can't destage fast.
Thanks,
.../Ed
--
Ed Wilts, Mounds View, MN, USA
mailto:ewilts AT ewilts DOT org
_______________________________________________
Veritas-bu maillist - Veritas-bu AT mailman.eng.auburn DOT edu
http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
|
|
|
