[OpenAFS] Re: failover 1.6.0pre2 dafs

Andrew Deason adeason@sinenomine.net
Sun, 27 Feb 2011 18:39:49 -0600

On Sun, 27 Feb 2011 20:45:24 +0100
Gémes Géza <geza@kzsdabas.hu> wrote:

> Another question: if I would allocate 2 or 3 separate pt and vl server
> machines what would happen if one or two of them would go off-line,
> from the point of view of afs clients?

You probably want 3. If you lose enough machines to lose quorum, you
will not be able to write to the database (for the vldb that means
releasing/moving volumes, etc; for the ptdb that means changing group
membership or adding/removing users, etc).

For 2 dbservers, you will lose quorum if the machine with the lowest IP
address goes down. For 3 dbservers, you will lose quorum if any 2
servers go down. Whenever the sync site goes down, you'll lose quorum
temporarily while an election is held (which can take a few minutes).

For read access: generally speaking, as long as any dbserver is
reachable from clients, they should be able to read data (which means,
they will be able to locate volumes). It may take a minute or two for
clients to notice which machine is actually up as they go through each
dbserver trying to contact one, but after that they should be okay.

Andrew Deason