You can easyly proof you tape theorie by makeing an backupset on the TSM
serverdisk 
and doing the same restore. There should be a significant difference if
that's true.
WR Stefan Holzwarth

> -----Ursprüngliche Nachricht-----
> Von: Mark Bryant [mailto:mark.bryant AT ZURICH DOT COM]
> Gesendet am: Donnerstag, 21. September 2000 13:19
> An: ADSM-L AT VM.MARIST DOT EDU
> Betreff: Re: Slow restore for large NT client
> 
> My view on the slow restore problem is that it is down to the tape
> technology. I've done quite a bit of testing with restores on 
> AIX, NetWare
> and NT and can say the following:
> 
> 1. I can rule out the network and server performance as the 
> bottle neck.
> Doing a full backup and restore will give comparable 
> performance and ADSM
> will run as fast as the network will allow. Also as fast as any other
> product (Arcserve, BackupExec).
> 2. Large filesystems containing large files will give a 
> reasonable restore
> performance. Large filesystems with lots of small files give 
> a terrible
> restore performance.
> 
> What I think is happening is this:
> Due to the incremental forever backup method the files are becoming
> fragmented on the tapes. A file changes so a new version is 
> written to the
> tape. The oldest version is then deleted  leaving a gap on 
> the tape. The
> problem with fragmented tapes is that the seek speed of the 
> tape drives is
> very slow. Some are better than others, I've found Magstar  3570's are
> quite a bit faster than DLT's. So when we come to do a full 
> restore the
> tape drives are spending most of the time searching rather than
> transferring data.
> Arcserve and the like do not have this problem as they are 
> generally setup
> for a weekly full, daily differential so are able to stream 
> data off the
> tapes in one big block and are only really limited by the 
> transfer rate of
> the tape drive.
> The probem with ADSM has really got worse over the last few 
> years due to
> the amazing growth in disk capacity/price. It is now becoming a real
> problem when we have these big fileservers going in.
> I'm not sure what the answer is. Some things that can help 
> are to make sure
> you are collocation on your tape pools and run regular reclamation to
> reduce the fragmentation.
>