[Beowulf] PetaBytes on a budget, take 2

[Mark Hahn]

> I'm curious, has anyone tried building one of these or know
> of anyone who has?

a guy here built one, and it seems to behave fine.

> Seems like a cheap solution for raw backup.

"raw"?  I think the backblaze (v1) is used for rsync-based 
incremental/nightly-snapshots.

but yeah, this is a lot of space at the end of pretty narrow pipes.

at some level, though, backblaze is a far more sensible response 
to disk prices than conventional vendors.  3TB disks start at $140!
how much expensive infrastructure do you want to add to the disks
to make the space usable?  it's absurd to think of using fiberchannel,
for instance.  bigname vendors still try to tough it out by pretending
that their sticker on commodity disks makes them worth hundreds of 
dollars more - I always figure this is more to justify charging 
thousands for, say, a 12-disk enclosure.

backblaze's approach is pretty gung-ho, though.  if I were trying to do
storage at that scale, I'd definitely consider using fewer parts.
for instance, an all-in-one motherboard with 6 sata ports and disks
in a 1U chassis.  BB winds up being about $44/disk overhead, and I 
think the simpler approach could come close, maybe $50/disk.

then again, if you only look at asymptotics, USB enclosures knock it
down to maybe $25/disk ;)