Hello Alessio and Gordon, thank you for answers.
Dsync-based architecture looks promising, but I would preffer to stay with GlusterFS for now as I also use it as a storage for other components.
So director is the way to go, I don't want to setup more than two nodes to keep this setup as simple as possible - so I will probably update to 2.2.19 and have director and backend on the same servers (and Dovecot instance).
I asked about poolmon, because I think that Dovecot should have some internal mechanism on how to recognize broken backend by default. But if it works nicely, I am going to use it as well :-)
At the moment, I cannot recognize the requirement for using lmtp over the directors. When using postfix for delivering e-mails to the backend, do this directly with an corresponding MX record.
I have two MX records of the same weight with postfix using dovecot-lmtp for delivery. So that's why I wanted to use LMTP over directors. Using lower weight for second MX is an option, but not truly master-master setup :-)
Filip
On 2015/12/06 02:31, Alessio Cecchi wrote:
Il 05.12.2015 10:42 Filip Pytloun ha scritto:
Hello,
I have recently setup mailserver solution using 2-node master-master setup (mainly based on MySQL M-M replication and GlusterFS with 2 replica volume) on Ubuntu 14.04 (Dovecot 2.2.9).
Unfortunately even with shared-storage-aware setting:
mail_nfs_index = yes mail_nfs_storage = yes mail_fsync = always mmap_disable = yes
With only these setting you don't solve the problem of shared storage.
..I have hit strange issues pretty soon especially when user was manipulating same mailbox from multiple devices at the same time.
Most issues was about corrupted indexes which was solved easily by just putting them on local storage of each node:
mail_location = maildir:/srv/mail/%d/%u:INDEX=/var/lib/dovecot/index/%d/%u
But I still hit issues like this one:
dovecot: lmtp(6276, user@example.com): Error: Broken file /srv/mail/example.com/user@example.com/dovecot-uidlist line 8529: UIDs not ordered (8527 >= 8527)
Which I am not sure how serious it is or if it's possible to solve or workaround?
You need Director for POP/IMAP and also LMTP so you can solve all "Broken file" and "corrupted indexes" problems.
Anyway because of the above and high possibility of GlusterFS split-brains, I have decided to setup Dovecot Director according to the docs [1] but I have a couple of questions:
- is custom monitoring still required? Poolmon [2] is 4 year old so I would suppose there's some progress since that?
For me poolmon works fine.
- it's not possible to have same backends and directors in Dovecot <2.2.17. I can backport newer Dovecot for Ubuntu Trusty, so this is not an issue, but..
Yes is possibile (also with < 2.2.17), create two instances, like dovecot and director, two config directory /etc/dovecot/ and /etc/director/ and bind on differents IPs.
- documentation states that it still doesn't work for LMTP [3]? Which is probably important for my setup, because both Postfix servers are using dovecot-lmtp for mail delivery so there can be still some issues (but probably less frequent?) when both servers will deliver new mails for one user at once. So do I really have to split directors from backends?
I'm running Director and backend on the same server for POP/IMAP, and in another configuration and Director for LMTP is on the same server (but with 2.2.19).
Anyone has experience with clustered Dovecot setup? Why is Dovecot behaving so bad when it pretends to be shared storage friendly? Are these issues only specific for older Dovecot? Or is there something wrong in my architecture design?
You need Director, Dovecot has not problems with shared storage, big installation are always using shared storage (like NFS).
Alessio Cecchi Postmaster AT http://www.qboxmail.it http://www.linkedin.com/in/alessice