Thomas Mueller schrieb:
> 
> >> > I tried to do that years ago but I believe this made all tapes that
> >> > were already written to unreadable (and I now have 80) so I gave this
> >> > up. With my 5+ year old dual processor Opteron 248 server I get
> >> > 25MB/s to 45MB/s despools (which measures the actual tape rate) for
> >> > my LTO2 drives. The reason for the wide range seems to be
> >> > compression.
> >> 
> >> Can anybody confirm or rebute this for 2.2.x? I'm currently fiddling
> >> with Maximum Block Size and a shiny new tape. It looks like 1M is too
> >> much for my tape drive, but 512K seems to work and it's making a huge
> >> difference: btape fill reports > 60 MB/s right at the beginning, then
> >> drops to abour 52 MB/s.
> > 
> > With
> > 
> > Maximum File Size = 5G
> > Maximum Block Size = 262144
> > Maximum Network Buffer Size = 262144
> > 
> > I get up to 150M MB/s while despooling to LTO-4 drives. Maximum File
> > Size gave me some extra MB/s, I think it's as important as the Maximum
> > Block Size.
> > 
> 
> thanks for providing this hints. just searching why my lto-4 is writing 
> just at 40mb/s. will try them out!
> 
> searching the "Maximum File Size" in the manual I found this:
> 
> If you are configuring an LTO-3 or LTO-4 tape, you probably will want to 
> set the Maximum File Size to 2GB to avoid making the drive stop to write 
> an EOF mark. 
> 
> maybe this is the reason for the "extra mb/s". 

Modifying the Maximum Block Size to more than 262144 didn't change
much here. But changing the File Size did. Much.

Anyway, 40 MB/s seems a bit low, even with the defaults. Before tuning
our setup I got ~75 MB/s. Are you spooling the data to disk or writing
directly to tape?

Ralf

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