Daniel Watts wrote: > Our system looks like this: > > [internet] > > [load balancer] [load balancer] > > | \/ | \/ A > [web] [web] [web] <---mysql cluster > > \ | / > [imap server] > > > > The web servers are all sharing their sessions which are stored in a > mysql cluster. This means that the user can connect to any web server > and still maintain their session. > > However we've just found another problem - attachments. The user > connects to webserver1 and clicks the Compose button. They then upload > an attachment onto webserver1 and compose their message. When they press > Send, the request actually (due to round robin dns) hits webserver2. > Webserver2 tries to load in the attachment but can't find it. > > We don't really want to be storing 30MB attachments in a database as > well and using a shared NFS attachment driectory introduces a single > point of failure (the NFS server). Can anyone think of any other options > we have? So, by examining your logic, isn't the MySQL server, where you are storing the sessions, a single point of failure as well? Webmail clustering is a bit complex when you think about parameters like that. If you are only distributing queries at the DNS-level, there is a way to make users stay at the same server, through clever redirecting. However, you will lose somewhat in balancing, and you might consider the redirecting point a "single point of failure" as well. If you use "pound" load balancer, or similar, then you can definitely stay at the same server in a session; this will also allow for some more clever balancing. But you might regard the pound server "a single point of failure" and will need to put more of them too! See how hard it can be? :-) Why isn't your load-balancer clever enough to make users stay at the same server? So, first of all, you'll have to provide more information about it. Alexandros ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 -- squirrelmail-users mailing list Posting Guidelines: http://www.squirrelmail.org/wiki/MailingListPostingGuidelines List Address: squirrelmail-users@xxxxxxxxxxxxxxxxxxxxx List Archives: http://news.gmane.org/thread.php?group=gmane.mail.squirrelmail.user List Archives: http://sourceforge.net/mailarchive/forum.php?forum_id=2995 List Info: https://lists.sourceforge.net/lists/listinfo/squirrelmail-users
