[sclug] Mirror disks across machines like distributed RAID?

Tom Carbert-Allen tom at randominter.net
Wed Jan 6 17:05:14 UTC 2010

On 06/01/2010 4:54, Dickon Hood wrote:
> : Even with a cluster of webservers they have to have access to the same
> : data so surely you've still got to have some sort of HA disc system?
> No point.  Replicate.  It's cheaper than a traditional HA disc system,
> arguably less complex than a DRBD setup, and almost certainly more
> performant: disc RTTs become important if you're cobbling a page together
> from multiple objects..
And what system of replication are you suggesting? DRBD is a replication 
system which does the exact job you describe and isn't complex at all.
> you will probably find that a cheap(ish) box exporting over NFS will work well for
> that sort of thing, and a full-blown multi-master, multi-head SAN setup
> overkill.
> Don't get me wrong: there are applications for which HA disc is absolutely
> required.  It's just it mostly isn't.
Well the OP requirement was for his NFS share to stay up when he wasn't 
at home. This is exactly the time when it's needed. There is no engineer 
on site to manually setup another box when he is out and DRBD is the 
easiest way I can think to make sure some dust build up in a cpu fan 
doesn't mean that after three years he can't get his data from home one 
day without driving back and restarting it.
Big corps with big money sites can afford to pay a guy to play poker all 
night waiting for a red light, most sites can't and most small business 
can't either, which actually outnumber the bbc millions to one.


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