[Veritas-bu] Where in NBU are drive settings (LTO-1 and LTO-2) tuned separatel y?

2003-12-05 16:08:55
Subject: [Veritas-bu] Where in NBU are drive settings (LTO-1 and LTO-2) tuned separatel y?
From: Joost Mulders <mail AT j-mulders.demon DOT nl> (Joost Mulders)
Date: Fri, 5 Dec 2003 22:08:55 +0100 (CET)
Hi Aren, 

Two notes on your question:

1. Media
Make sure you are using LTO2 media in your LT02 drives. With IBM drives (and I 
think the others as well), using LTO1 media in an LTO2 drives reduces the max. 
throughput to 20MB/s. 

Make sure you have /usr/openv/netbackup/db/config/SIZE_DATA_BUFFERS file on 
media server(s) with a value of 262144 (256K) in it. This file controls the 
of the data buffers yadiyadiyadi, but also the blocksize used to transfer data 
to the drive. Using "big blocks" lowers SCSI/FC bus overhead (each block has to 
be sent and acknowledged) and it improves the efficency of the compression 
algorithm in the drive: the larger the block, the more "similar" patterns can 
found and compressed.

The above is true for all tapedrives. There are no LTO2 specific knobs.


>NBU 3.4.1 Master:HP-UX 11i three-way service guard cluster Library:ADIC
>scalar10k IBM Ultrium drives:[email protected], [email protected] same cabinet. We have just
>benchmarked our new LTO-2 drives and they are NO FASTER than the LTO-1
>drives. Are there separate tuneables for the new drives we are not looking
>at?  Buffer settings, something undocumented perhaps?  We have a 3GB (bound)
>FC ethernet connection on the media server so I don't think it's a network
>bottleneck, disk is XP-512 (rebadged Hitachi) screaming fast disk.  Tested
>same class on each type of drive, identical runtimes. ??? Thank you experts.
>     Aren M. Parisi *
> Information Technology
>  Western Wireless Corp.
>(425)313-5225 mob.(206)795-6631
> Where are we going and why am I in this handbasket?

Long may you run.