Hello, Actually, there is no SAN server. The SAN is to be implemented with fiber channel devices. The imap servers will have a fiber channel interface which is connected to a fiber channel switch. Also connected to the fiber channel switches are the RAID units with the actual storage.
As for the load balancing, we have been using it for a while and are quite comfortable with what it does and how it works. And why have partner IMAP servers replicating work when having one machine do the work and the other see it immediately. In other words, the shared file system implemented on top of the SAN ( shared file system does not equal SAN ) sorta does the replication. In a very real sense you have one hard disk mounted on two machines. Once one does the file system update the other can see it. The trick is, and hence my question, how does one handle access to prevent corruption. Is cyrus written so that what the shared file system provides is sufficient, or does the application need to be made aware of the possibility of two processes on two different machines writing to the one disk? And yes, we need to have more than one imap server. I drew the picture below only showing two because that was easy in ASCII. In reality we will probably have at least four. Each being managed by the Resonate load balancing service and all connected to the same shared file system. Regards, Earl Shannon -- Systems Programmer, Computing Services, Information Technology NC State University. http://www4.ncsu.edu/~ershanno Sean Witham wrote: > > Earl R Shannon wrote: > > > Hello, > > > > We would like to use a shared filesystem. Will ALL the accounts on > > each server. Then we would use a load balancing package ( Resonate ) > > in front of the servers. Should one server fail the service would > > continue. > > > > Network > > /\ > > / \ > > / \ > > / \ > > ResonateMaster-----ResonateSlave > > |\ /| > > | \ / | > > | \ / | > > | \ / | > > | \ / | > > | \/ | > > | /\ | > > | / \ | > > | / \ | > > | / \ | > > | / \ | > > |/ \| > > cyrusbox1 cyrusbox2 > > \ / > > \ / > > \ / > > \ / > > \ / > > \ / > > San ( shared filesystem) > > > > > > When you look at that you have to ask if the San server and the load > balancer are reliable enough to justify two cyrus servers or if you > would be better off with just one cyrus server ? What you really want is > a cyrus (or similar server) that can replicate updates between two > partner servers. Or is you san really a virtual server that consists of > a cluster of replicating units ? > > --Sean > > --Sean -- Systems Programmer, Computing Services, Information Technology NC State University. http://www4.ncsu.edu/~ershanno
