Quoting "Eric Rostetter" <rostet...@mail.utexas.edu>:
Quoting Rick Romero <r...@havokmon.com>:
They claim to be real-time, and with kernel hooks into
reads/writes, it seems promising to run on top of the OS..
Yes, but that doesn't mean it will work in the cluster environment...
It also says things like:
There are different types of file locks. In addition to these differences,
each OS has its own set of rules regarding file locks as well. FRP's
replication of locked files will vary in relation to the way the OS treats
these types. However, one rule is consistent throughout all operating
systems in that exclusive file locks will prevent FRP from replicating data.
See that last line there??? Want to bet something in the mail setup
(MTA, dovecot, system jobs like backup, etc) put an exclusive lock on
files from time to time?
Again, a fine backup system, and depending on your needs it might be
okay for a failover setup, but not for an active-active setup. For
that you need a lock manager, which they promise "in the future" but
don't deliver yet...
I thought the entire reason (ok not the _entire_ reason but..) for
Maildir was to avoid locks and allow easy concurrent access to a
mailbox through many different applications.
From DJB's page: http://cr.yp.to/proto/maildir.html
Why should I use maildir?
Two words: no locks
So while I do agree that file locking is a possible problem in an
active/active setup with FRP, I think it's possible - as long as the
admin is aware of the risks. So for backup purposes, to avoid locks
for example, use ZFS snapshots.
I'm not even a user of FRP at this point, but it's something that
intrigues me for active/active because of it's OS independence. I
want ZFS. I really enjoy ZFS. I already have active/passive with zfs
sends, I want to step it up :)
Yes, there are definitely things to be aware of. I'm not sure if this
is the place to hash it out, but I think that while it's not a cheap
solution it may fit MY environment - and possibly others who use
Maildir.
I guess everyone is as cheap as I am and hasn't set it up yet :)
Rick
