Marcelo et al, > -----Original Message----- > From: info-cyrus-bounces@xxxxxxxxxxxxxxxxxxxx > [mailto:info-cyrus-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of > Marcelo Maraboli > > thanks for the input, I know wishing 100% is only available > with a gooooogle size amount of money ;), but I am looking > for a CYRUS IMAP server solution similar to a load balancing > web server farm...i.e: > > - a Load balancing server (PEN in Freebsd if you like) that > will direct an IMAP session to ANY of a group of IMAP servers, > all of which have access to a central storage of user MBOXs. > > So if any of the IMAP (backend) server dies, the load balancer with > automatically not forward any new requests to that server > and users won´t notice any downtime.. > > this is diferent from Andrew´s solution number 1, since ANY of > the backend IMAP server should accept connections for ANY user. > > examples: > http://siag.nu/pen/vrrpd-linux.shtml > http://redundancy.org/fbsd_lb.html > > can IMAP be set up this way ?? > > regards, > This need is why I suggested beefy servers rather than the Murder, which I don't consider sufficiently highly available due to actually being a number of discrete servers at the back end. Great for load balancing, useless for instant failover in case of server loss. In short, as I understand it Cyrus cannot be set up this way. Only a single machine can have write privileges to the mailboxes database at a time. The only way I can see to do this is to use NFSv4 which is supposed to get the locking correct. Then, assuming the database is closed between changes (can a developer please confirm whether it is kept open by master or not?) you should be able to run multiple IMAP servers over the same filesystem stored on a NAS (network-attached storage, as opposed to SAN). That is the only way I can think of to do what you are after. You would need two NAS boxes, ideally in separate buildings, with live mirroring (10 Gb fibre or copper connection between) and a bunch of cheap servers in each building all load-balanced. You should be able to lose a complete data centre and just keep running at 50% capacity as long as your network is properly routed (with redundancy in case of an idiot with a spade cutting through your fibre of course). It's expensive, but it should work if the database is not held open. If it is, then you need to look at a different email product. Cyrus is a great server, but if you need five 9s reliability then you have to pay for it. You could always look at an appliance - dedicated hardware is often more reliable and at least if it goes down you can scream at the vendor and cover your butt that way. Regards, Sarah Walters ---- Cyrus Home Page: http://cyrusimap.web.cmu.edu/ Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html
