> 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. -- "... a serious depression seems improbable; [we expect] recovery of business next spring, with further improvement in the fall." Harvard Economic Society, November 10, 1929
