> On Monday 17 August 2009, Cyrille Bollu wrote:
> >> I wouldn't put the holding disks in raid.
> >
> >Hu hu... Interesting... I have a 4 disks RAID-0 holding disk, and it
> > isn't fast... I always wondered if I should use seperated (non-RAID)
> > drives...

To drive an LTO-4 your holding disk needs to read somewhat over 100MB/sec 
sequentially, which requires at least 2 drives striped, but should be easy 
enough with any modern raid controller or software raid. 

Complicating this, it may also need to write at similar speed, 
simultaneously, which introduces a random access element and ups the demand 
considerably. I would think you would probably want at least 4 big SATA 
drives striped together to reliably feed an LTO-4 drive at full speed. 
Conveniently, this could also give you over 5TB of very cheap holding disk 
space.

Also, unless you're backing up exclusively large files over a fast SAN link 
(faster than Gig-E), I doubt you could get anywhere close to full tape 
performance without a holding disk.


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