Distributed network RAID

[Bart Silverstrim]

Jason wrote:
> couple of options in easiest to most difficult order.
> 
> if don't mind having access to a filesystem on only one node at a time,
> just use NFS to mount the filesystem.

Thought NFS was more of a file-sharing thing so the data isn't really 
redundant?

I was looking to have a copy of my data in a second location so I can 
access it if the primary system/hard disk dies on me.

> rsync.  Run it every minute between the two hosts.

I'm thinking this could be error prone with files that are open or 
half-copied at the time Rsync runs, plus rsync, if I recall, may suck up 
the processor during the process if it must look at a large amount of 
files and calculate diffs.

But then again, I thought rsync could copy portions of files if only a 
section changes, and whenever I use it rsync copies the entire file 
over. Maybe I'm doing something wrong.  I don't know.

> gfs or another clustered file system. Lets you use the same block device
> on two machines at once.
> 
> Get crazy with iscsi and gfs or maybe nbd.  This would most likely fail
> in a very spectacular way when you are least able to handle a failure.

This is for a home setup, so I don't think I can afford an iscsi/NAS for 
failover :-)

NBD sounds closer to what I was looking for, but I've never heard of 
anyone using it before.  Sounds like you've use it before, though, since 
you don't appear to like it too much...care to share 
information/experiences on that?  I see NBD is supposed to be part of 
the base Linux kernel, from just glancing over some material on it.