Andrew
thanks for the "scalable" Cyrus solutions, but I´m wondering
what can be done for Availability solutions ??
What if an IMAP server dies (we had this happen) ??
We have a Solaris Server with a RAID5 disk array storing the
MBOX, but the server died....so downtime was a bit huge..
I wan to build a 100% available IMAP solution...is there any?
regards,
Andrew Morgan wrote:
On Fri, 17 Nov 2006, Igor Zhbanov wrote:
2006/11/17, Adam Tauno Williams <adam@xxxxxxxxxxxxxxxx>:
> Yes, I know how failover cluster works. But what if one server
> (active) can't process such a load? Suppose, we plan to have 100 000
> users working actively with mail. I understand that it is possible to
> use one monstrous server to take all of the load, but I am interested
> in load-balancing solution on relatively inexpensive servers.
(a) SANs are not that expensive.
(b) SANs are *WAY* *WAY* more reliable than *ANY* storage solution you
can build yourself for the same amount of money. If you really don't
believe that you need to lay of smoking the good stuff. And (b.1) - if
you have that many users but can't afford a SAN...
(c) Then there is Cyrus replication and there is GFS. There was long
thread on Cyrus IMAP, HA, & GFS just back in October.
> And what
> about slow anti-viruses for 100 000 users' mail? Or to use
> load-balanced front-ends connected to single SAN and connected to
> anti-virus load-balanced cluster? :-)
It doesn't require a cluster to load balance SMTP, traditional and well
established technologies will do that for you. Setup multiple SMTP
servers and publish multiple MX records.
Yes, I can use DNS-based load-balancing to spread load to several
frontends. But what about backends? :-) How to balance load for them?
There are basically 3 known solutions to building a scalable Cyrus system:
1. Cyrus murder + Cyrus replication. Cyrus murder distributes mailboxes
across multiple backend servers. The murder backend servers could use
local storage, or be connected to a SAN, non-shared file system. The
murder frontends (you can run as many frontends as you want) accept
incoming IMAP and LMTP connections and route them to the correct murder
backend server. You could use DNS round-robin to load balance
connections between the murder frontends, or you could use something
more sophisticated like LVS or a hardware-based network load balancer.
Use Cyrus replication to keep a backup copy of each murder backend.
2. Cyrus replication + perdition/nginx. Manually distribute your
mailboxes between multiple Cyrus servers (in a non-murder
configuration). Use Perdition or nginx to route incoming IMAP
connections to the correct server. Use Cyrus replication to keep a
backup copy of each murder backend.
3. Cyrus + SAN + clustering. Use multiple servers in a cluster,
connected to a SAN. Several different people have attempted this
according to recent mailing list postings here. The only successful
cluster I'm aware of was a Tru64 cluster.
Andy
----
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
--
Marcelo Maraboli Rosselott
Jefe Area de Redes y Comunicaciones (Network & UNIX Systems Engineer)
Ingeniero Civil Electronico, CISSP (Electronic Engineer, CISSP)
Direccion Central de Servicios Computacionales (DCSC)
Universidad Tecnica Federico Santa Maria phone: +56 32 2654071
Chile. http://www.usm.cl http://elqui.dcsc.utfsm.cl
----
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
