Questions about hardlinks, alternate storage and compression

Gionatan Danti g.danti at
Mon Jun 29 09:20:34 UTC 2015

Hi all,
any ideas?

Especially point n.1 (no hardlink when sending the same email to 
multiple addresses) confuse me a bit. Searching in old messages I even 
stumbled on some users stating that, using Dovecot LMTP server, they 
achieved what I want (one messagge, multiple hardlinks), but I am 
_already_ using LMTP with no avail...


On 27/06/15 18:18, Gionatan Danti wrote:
> Hi all,
> I have some questions about hardlinks, alternate storage and
> compression. I already scanned the list for related information and I
> have an idea of how things works, but I would like to have a definite
> answer.
> System spec:
> - CentOS 6.6 x64
> - dovecot-2.0.9-8.el6_6.4.x86_64 RPM package/version
> - sdbox mail store
> 1) About hardlinks: when sending the same message to two different
> recipients, I see that the two u.x files are created as two different
> files. Diffing them, I see that the only difference is a single char
> (see [1] for an example). My questions are:
>    a) it is possible to tell dovecot to create a single file + a single
> hardlink (linkref=2)? As other IMAP servers support that features (eg:
> Cyrus, CommunigatePro, etc) I am wondering if I missed something in
> configuring dovecot...
>    b) If it is not possible, can I run a script that compare the various
> files and substitute equal ones (minus the changing line) with
> hardlinks, or it will confuse dovecot? As a side note, why the changing
> line ever exists?
> 2) About alternate storage and compression: actually, I use a single
> mail_location without compression. I would like to have an alternate
> storage and to enable compression on it only, leaving the main location
> without compression. I if understand it correctly, it _should_ be done
> using a command similar to "doveadm -Dv -o "plugin/zlib_save=gz" altmove
> -uu testuser sentbefore 8d". I'm right thinking that it should work? I
> will really end with a primary uncompressed mail store and an alternate,
> zlib-compressed one?
> Thank you all and sorry if I did some naive questions.
> [1]
> 63c63
> < G2fd0811c64be8e553d970000eaa8309f
> ---
>> G2ed0811c64be8e553d970000eaa8309f

Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. -
email: g.danti at - info at
GPG public key ID: FF5F32A8

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