Jonathan Tripathy put forth on 1/14/2011 12:22 PM: > > On 14/01/11 18:13, Stan Hoeppner wrote: >> Jonathan Tripathy put forth on 1/13/2011 7:05 AM: >> >>> What does everyone think of a DRBD + GFS2 idea? >> I wrote up a detailed response to the same question on the Dovecot list >> yesterday, in fact, in response to you. > You did indeed, thanks >> Why are you running the same thread on >> both mailing lists? >> > > There's different people on each list. It's nice to get views from lots of > different people. Especially when I think that Dovecot causes more issues with > shared storage than postfix (according to the respective wikis anyway)
Of course it has issues with shared storage. It's an IMAP server and it uses indexes for increasing performance. Sharing index files between cluster node instances of an imap daemon will always be painful until you move to an actual database engine for the indexes which removes all the current locking headaches. Postfix is an SMTP server. It's a completely different beast. It never accesses an email once it's delivered, so no need for indexing. SMTP was designed in a way that allows massive parallelism to shared storage with few gotchas. IMAP was not. SMTP deals with messages while they're "in flight". IMAP deals with messages primarily AFTER they're in permanent storage, i.e. a mailbox. Coordinating multiple systems accessing the same shared mailbox store is not an easy task. This is not limited to IMAP servers either, but many applications that folks want to scale, but whose architecture doesn't easily allow it. IMAP wasn't written with scaling the workload across multiple hosts in mind. -- Stan
