RE: tape speeds, TSM and pase

[rob@xxxxxxxxx]

TSM under PASE defeats any advantage you may have with direct, lan or 
whatever.  We tried a 3582 LTO 2 attached via fiber and got exactly the 
same speed as a 3581 LTO 1 attached via cable.  When using it with TSM 
under PASE the only advantage the 3582 lto 2 gives you is higher tape 
capacity.

Rob Berendt
-- 
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





Chris Bipes <chris.bipes@xxxxxxxxxxxxxxx> 
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03/22/2005 04:56 PM
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RE: tape speeds, TSM and pase






Direct attached will always beat LAN speeds unless you have some dedicated
High Speed Fiber between your backup server and iSeries to be backed up.

Chris Bipes

-----Original Message-----
Rob

I'm just starting a project to go down this road so it is interesting that 

you posted the performance figures - I had been wondering whether this was 

any better these days.

TSM has always been much, much slower in terms of tape speed than native 
AS/400 tape functions at least in my experience so what you are seeing 
does 
not surprise me in the least. One of the arguments to defend this I always 

used to hear was that it didn't matter because you were always going to be 

doing incrementals anyway so the data volumes would be much smaller after 
the first save. This theory really fell apart on a development box where 
there were new copies of data and new libraries created all the time but I 

could probably accept that this is not typical. One of the system I was 
managing also had a monster file that used to change every day and loads 
of 
files written to the IFS which were required so even the production 
incrementals were highly volatile and caused some issues.

Fortunately I will not be running the server on the iSeries (I don't think 

I ever want to have to do that again) so the PASE limitation is not likely 

to bite me at least as far as the server API's go, but I am wondering what 

the performance will be like throwing the data across the network to (I 
think) a 3583  attached to a pSeries.

Just so I have something to compare against later on, how did you got 
about 
measuring the throughput ?
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