[Dovecot] Enabling SIS (single instance storage)

Charles Marcus CMarcus at Media-Brokers.com
Fri Dec 27 20:32:22 EET 2013

Ok, didn't find much on this...

The bottom of /etc/dovecot/conf.d/10-mail.conf has the following settings:

#mail_attachment_dir =
#mail_attachment_min_size = 128k
#mail_attachment_fs = sis posix
#mail_attachment_hash = %{sha1}

all of which are apparently the defaults according to doveconf -d output 
- so no need to set them explicitly, unless I want to change them, right?

So, enable the first one - but - the comments don't say anything about 
supporting variables. I'm assuming you can, otherwise all attachments 
for all domains would be in a single directory, which some admins might 
not like (I wouldn't)... so hopefully I can just set it to this:

mail_attachment_dir = /var/vmail/%d/.attachments

So how does this work during conversion? Users still on maildir simply 
don't engage it? But as users are converted to dbox, all attachments are 
de-duped, and then new mails coming in with attachments (for converted 
users) are de-duped at delivery?

The wiki could do with a bit more on enabling and implementing it, 
especially what to expect when enabling it for the first time on a 
production system and what to expect along the way when converting 
existing users...


Best regards,


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