Poor write performance on LTO3 drives

[Bruno_Bossier]

Netbackup 6.0MP2
Master server : Sun V240 with 1cpu and 1GB memory
Tape library : Sun StorEdge L500 with 2 LTO3 drives

Test : backup of one 5GB file which resides on the internal disks

Throughput : 12MB/sec

This is pretty low. Any ideas ? Should adapt /etc/system settings (shmmax, ...), use the Netbackup data buffers parameters, will adding memory help, .... ?

Thanks,
Bruno

[Stumpr2]

yes to all...

Please read this document. It will answer ALL of your questions.

VERITAS NetBackup (tm) Enterprise Server / Server 6.0 Backup Planning and Performance Tuning Guide for UNIX, Windows, and Linux

http://ftp.support.veritas.com/pub/support/products/NetBackup_Enterprise_Server/281842.pdf

[Bruno_Bossier]

Yes, I know that document. I already added the default /etc/system settings as described in the manual, but no change.

Someone from Symantec told me yesterday that there is some kind of command that you can use to request the blocksize or buffer size (don't recall exactly) from the tape library and that I should adapt Netbackup accordingly.

Any ideas ?

[Chia_Tan_Beng]

> Someone from Symantec told me yesterday that there is
> some kind of command that you can use to request the
> blocksize or buffer size (don't recall exactly) from
> the tape library and that I should adapt Netbackup
> accordingly.
>


Its good to understand the I/O blocksize of the tape device but I think they shouldn't be the bottleneck. Have you verified that the wait time for empty buffer and wait times for full buffer in bpbkar & bptm logs are healthy?

If you really feels that the culprit is some where along tape device path, do a quick verification by backing up to a disk storage unit (different disk from the source data).

PS: There're also a number of other system parameters mentioned in the document in Bob's reply. Try looking at those.

[zippy]

Bruno,

There are boat loads of stuff you can do.

First download a UNIX guide for you server.
http://ftp.support.veritas.com/pub/support/products/NetBackup_Enterprise_Server/

Fix your kernel, this is link for HPUX, it gives you an idea, the data you need will be in the UNIX guide from the link above.

http://forums.veritas.com/discussions/thread.jspa?messageID=4431070鳞

1 Patch your servers O.S
2 Check your Firmware on ALL you hardware including the tapes drives.
3 Check your LAN cards - Switches (they must be a the same speed)
4 Patch Netbackup
5 Check HBA cards and all Switches (Make sure they are at the same speed)
6 Do you have a FIBRE - SCSI router? Check the setting on this appliance.

All done?

Now check the performance settings on the Master server.

1 Check the STORAGE UNIT settings MAX Fragment Size, Max Multiplexing Per Drive.

Remember the tape drives inherently will ALWAYS be faster than what you server can deliver, we are dealing with BUS I/O, HBA and LAN card I/O, server processing speed, Switch Settings.

JD