On 05 Mar 2015, at 12:46, Patrick Westenberg <p...@wk-serv.de> wrote:
>
> Hi everyone,
>
> can anybody explain the difference between Dovecots fast sync and full sync
> in replication mode?
There are actually 3 dsync modes, all explained in doveadm-sync man page:
o Full synchronization (-f parameter) scans through all
the
messages in all the mailboxes. This guarantees that
every-
thing will be synchronized, but it's unnecessarily slow
for
incremental synchronization.
o Fast synchronization (default) first attempts to find
mail-
boxes that have changed, and synchronize only those.
This
is done by checking the mailboxes' metadata (NEXTUID
and
HIGHESTMODSEQ). Usually this works fine, especially
with
one-way synchronization, but if both sides do exactly
the
same number of changes, the metadata may end up
containing
the same values even if the changes were different.
o Stateful synchronization (-s parameter) is the most
effi-
cient way to synchronize mailboxes. It relies on having
the
earlier dsync run's state saved somewhere and being
passed
to the next dsync run. Based on this state dsync can
send
only the changes that happened after the previous dsync
run.
As long as the state or the mailboxes aren't corrupted
this
algorithm should work perfectly. The replicator
process
uses this internally to perform most of the
synchronization.
