[ENBD] Load sharing with enbd?

[Peter T. Breuer]

"Also sprach Daniel Steen:"
[Charset ISO-8859-1 unsupported, filtering to ASCII...]
> Sorry.  Let me try and be more clear.  We have two web servers which we
> do load sharing across using simple dns round robin.  Currently they
> basically run independently of each other and are kept in sync through a
> combination of (very nasty) rsync scripts.  This is done more or less
> "live", but is not as reliable or as robust as we would like. 

The standard way this is done using raid is to have two partitions on
each server. Partition 1 is paired with the nbd-exported partition 2 of
the other server in a raid-1. That raid-1 device supports a file system
which is exported to the other server via nfs.

The situation is symmetrical. When one server dies one loses the remote
mirror of partition 1, and partition 2 is the mirror of the
dead server's partition 1. That allows one to continue happily on (one
has to shift the IP address of the dead server to the live one).

There are heartbeat scripts to handle that sort of thing. Some should
be in the distributed enbd archive.

Peter