2008/11/25 David McBride <dwm@xxxxxxxxxxxx>: > On Wed, 2008-11-12 at 17:44 +0800, Achievement Chan wrote: > >> I've setup a courier-imap server which store the email data in Maildir format. >> The mailbox are saved under a LUN in ISCSI SAN. > > I have no experience running the Courier IMAP server. However, the > Dovecot[0] IMAP/POP server implementation -- which maintains its own > indexes of mbox / maildir contents -- may provide better performance in > this configuration. > > Cheers, > David > > [0] http://www.dovecot.org/ > -- > David McBride <dwm@xxxxxxxxxxxx> > Department of Computing, Imperial College, London > > -- > Linux-cluster mailing list > Linux-cluster@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/linux-cluster > I've tried both Dovecot & Courier using maildir storage mounted on GFS. Both server perform a lot slower on GFS compared to NFS even though GFS has smaller overhead. Maildir was designed for "lockless" filesystem. It does its own checking and take extra steps to make sure that the file is not being used by other process. These extra step is not necessary on GFS file system. Maildir also do a lot of stat() & readdir() system calls which considered to be very expensive system calls for GFS & other cluster file system. Slow performance issue will be noticeable if your users keep an average of 1000+ email in their mailbox (especially if you have lots of these users) Changing maildir to mbox may helps reducing IO wait and increase mail server performance, but mbox format have file locking issue and prone to corruption. My ideal way is to mount maildir on ext3 filesystem and scale horizontally to different servers. eg :Server A hold & serve users with last user_id 0 to 3, Server B hold & serve users with last user_id from 4 to 6m, Server C hold & serve user with last user id from 7-9 These can be achieve with extra settings on your MTA to direct mail to the right server, and using perdition proxy to direct IMAP/POP to the right server. Regards, Rianto Wahyudi -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
