Hello Postmaster,

for a decade we have been using Dovecot successfully as IMAP server at Augsburg University.

Now we face the decision to switch from separated SAN storage to mirrored SAN storage by means of the usual combination of dovecot director and dovecot replicator (CentOS 7, Dovecot 2.2.36).

Dovecot director runs on four virtual machines (4 cores, 4 GB memory). The replicated storage is handled by two HP servers with 2 Xeon(R) CPU E5-2620 (6 cores) and 32 GM memory. The network relies on 2 x 1 GBit Ethernet bond and two redundant 4 GBit SAN-fabrics.

Our concerns, (1) is this equipment suitable? We are talking here about 25.000 mail accounts (LDAP) with 7 TB mail storage (mdbox) and in peak periods 10.000 parallel Dovecot processes and (2) what are adequate settings for director_user_expire, replication_max_conns and replication_full_sync_interval?

Loosing mails is unacceptable as well as users stumbling upon mails with the recent flag set which were read and deleted yesterday.

Who is using dovecot director and replicator and is willing to share settings and operational experience?

Thanks in advance

++ Michael Westerburg

-- Dr. Michael Westerburg

Universität Augsburg Rechenzentrum 86135 Augsburg

Telefon 0821/598-2004 Telefax 0821/598-2028 michael.westerburg@rz.uni-augsburg.de https://www.rz.uni-augsburg.de