Hi Kristopher --

If the drives in your SAN are SATA, then there are severe performance
issues with multiple threads.  I have been fighting disk-based
backups since spring 2005, and have had to use scripts for optimizing
backups and staging them to tape because the built-in Veritas
features for disk-based backups just don't work for me.

If anyone in this list has better news for Kris, I'm interested in
hearing it too...

>
> --__--__--
>
> Message: 2
> Subject: [Veritas-bu] LTO3 Buffer Setting Recommendation - NEW QUESTION
> Date: Tue, 27 Sep 2005 12:56:14 -0500
> From: "Williams, Kristopher L" <kris.williams AT hp DOT com>
> To: <veritas-bu AT mailman.eng.auburn DOT edu>
>
> Hello all,
>
> So I've started the long path of trying to get good performance out of
> my LTO3 drives.
>
> Let me start by saying my master is Win2k SP4 running NBU MP3. The media
> server is Win2k3 running NBU 5.0 MP3 with a 1 dedicated fiber channel
> card for the LTO3 drive (connected through a brocade SAN switch).
>
> This server has 4 2tb disks coming off of dedicated HBA's from a HP disk
> subsystem. I ran a multistreamed backup from 3 disks to the one LTO3
> drive and was only able to get about 15mb per second per stream. This is
> only about 45mb total throughput to the tape drive.
>
> I have this message in the bptm log so I don't think increasing the
> amount or size of buffers will help because it doesn't appear the server
> can fill them quick enough.
>
>  <2> write_backup_completion_stats: waited for full buffer 122203 times,
> delayed 124245 times
>
> If I map everything out, I can see the data coming from the subsystem
> switch port going to the disk HBA in the server, then going out the tape
> HBA in the server and hitting the tape drive. All the numbers remain at
> the 45-50mb per second.
>
> Is this just a simple exercise of breaking my 4 2tb disks down into
> smaller 500gb disks and running more streams to my tape drive? Any one
> have any suggestions or watchouts?
>
>
> Thanks,
>
> Kris
>
>
>
> -----Original Message-----
> From: veritas-bu-admin AT mailman.eng.auburn DOT edu
> [mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu] On Behalf Of stefanos
> Sent: Tuesday, September 27, 2005 10:37 PM
> To: Williams, Kristopher L; veritas-bu AT mailman.eng.auburn DOT edu
> Subject: RE: [Veritas-bu] LTO3 Buffer Setting Recommendation
>
> Microsoft doesn't support buffers more than 64k.
> But all new fibre card's drivers can accept more buffers.
>
>
> -----Original Message-----
> From: veritas-bu-admin AT mailman.eng.auburn DOT edu
> [mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu] On Behalf Of Williams,
> Kristopher L
> Sent: Tuesday, September 27, 2005 3:15 PM
> To: veritas-bu AT mailman.eng.auburn DOT edu
> Subject: [Veritas-bu] LTO3 Buffer Setting Recommendation
>
>
> Hello,
>
> Does anyone have a SIZE_DATA_BUFFERS / NUMBER_DATA_BUFFERS
> recommendation for LTO3 on Windows2k3?
>
> I know the first response will be to create the bptm log and try
> different things. I'm just looking for maybe a good starting point to
> which I will then fine tune.
>
> Details:
>
> NBU 5.0 MP3
> HP LTO Gen 3
> SAN Media Server: DL580 G4
>
>
>
> Thanks,
>
> Kris
>
--kathy