DragonFly users List (threaded) for 2009-01
DragonFly BSD
DragonFly users List (threaded) for 2009-01
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RAID 1 or Hammer

From: "nntp.dragonflybsd.org" <mneumann@xxxxxxxx>
Date: Mon, 12 Jan 2009 18:42:57 +0100


I'm curious if RAID 1 (mirroring) really helps to protect data loss. Of course if a whole disk "dies", RAID 1 has the advantage that
I have an identical copy. But what happens if only a sector of one disk
contains bad data. How can the RAID controller decide which is the
correct sector? Or would the disk detect such a case and return an error?

Instead of mirroring the disk on the block level, wouldn't a Hammer mirror (to a second disk) provide the same degree of data protection?
Of course it wouldn't provide the automatic fail-over a RAID 1 setting
provides, and there would be no improvment for reading blocks, but on the other hand it would stress the disk less, e.g. by mirroring only every 5 minutes (don't know if that matters at all).

The background is, that I am planning to spend my old server (running FreeBSD) a new huge disk and replace it with DragonFly :). The main reason to use DragonFly for me is to ease backups, which right now is a real pain (using rsync and hard-linking). ZFS would of course also provide that, but I assume that Hammer runs better on a P4/i386 with not too much memory.



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