On 2013-08-26 at 14:12 +0800, boyd yang wrote: > Would you please share your solution for Exim4 cluster?
How far up do you need to scale? 1,000 users? 1,000,000 users? 500,000,000 users? The appropriate solution varies depending upon where you want the bottlenecks to be, how much you're willing to spend, how you want to handle failure modes, etc. For instance, do you need to have replication with geographic diversity across a dozen datacenters, ensuring that no user's two primary locations are shared-fate for "common" (non-extinction-level) natural disasters? Or do you have one datacenter and only 10,000 users, so that one high-end storage array providing NFS will mostly work? NFS has problems in that it guarantees Unix filesystem semantics, with visibility of writes being immediate, rather than a postbox where you only need writes visible atomically before/after the message. The storage format chosen will significantly impact the filesystem burden. Something like Maildir scales well for small installations (five figure counts of users, perhaps into six figures with some heavy hacks). There are folks who use some of the Maildir++ hacks with Exim support, to ensure that appropriate data can be determined without having to hammer the filesystem, and by appropriately choosing IMAP and POP3 support which uses the same hacks. But ultimately, using a general purpose filesystem's directory structure as your locking mechanism will hit limits which get expensive to mitigate and constrain your technology choices. But hey, if you're small enough, it makes all the locking issues "someone else's problem" (the kernel's) and the simplicity makes it nice to reason about. Ultimately, you're asking for free systems architecture advice, which is something that people make a living working on. Without being more open about what you're working on, what you're trying to achieve, what the constraints are, and why you're trying to build an Ultimately Scalable Mailsystem without employing someone experienced to do the work, you're not likely to get very far. -Phil -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
