Re: [Nbd] 10 TByte partition

[Wouter Verhelst <w@...112...>]

Hi,

On a side note:

On Sat, Dec 11, 2010 at 01:27:45AM +0100, sf@...850... wrote:
> My setup: three old identical dual Xeon servers with six new 2TB SATA
> disks each.  Each server provides a 10TB RAID5.  Via nbd, those three
> 10TB partitions shall form a net RAID5².

That might not be the smartest thing to do, as RAID5 is a rather slow
setup. Remember, every time you want to write a stripe, you have to read
the other two stripes, calculate the checksum, and then write out two
stripes again (the checksum and a data stripe). Compare to RAID1, where
all you need to do is "write two stripes", and you'll quickly see that
RAID5-on-RAID5 might not be the best move.

Additionally, if pricing is your main concern, remember that the higher
load of the read-read-write-write cycles is not unlikely to cause the
disks to fail sooner.

I would recommend using RAID1 instead. It'll require more hardware but
it's faster (especially in software RAID) and does not strain your
hardware as much.

-- 
The biometric identification system at the gates of the CIA headquarters
works because there's a guard with a large gun making sure no one is
trying to fool the system.
  http://www.schneier.com/blog/archives/2009/01/biometrics.html