[Dovecot] dbox support state

[Bill Boebel]

On Fri, December 22, 2006 2:14 am, Steffen Kaiser <skdovecot at smail.inf.fh-bonn-rhein-sieg.de> said:

> On Thu, 21 Dec 2006, Timo Sirainen wrote:
> 
>> One optimization left for it would be to not store flags and keywords to
>> the dbox files at all, but keep everything in index files. Once I get
>> that implemented, I'll start benchmarking it. Of course the problem with
>> that is that it relies on index files completely then.
> 
> IMHO this is not good for disaster recovery and makes life needlessly hard
> in such case. Esp. when both files become out-of-sync, you need a cunning
> tool to re-construct any good state, rather than a simple "REINDEX". This
> should apply to each kind of "index" file. Also, consider upgrades to
> newer index file formats etc.pp.
> 
> Are there really that many writes of message attributes? I mean, there is
> only an improvement because you have just one write into the indexes
> rather than two, one to the indexes and one into the message.
> You've wrote that you reserve space for the flags in mbox, in case they
> get updated, so you reduce the probability to rewrite the whole mbox for
> each flag. Doing so should apply to dbox as well?

It should be an option.  Big mail systems can benefit from this optimization, but many systems may not see anything noticeable.

You can do a lot of cool things with your storage once you're dealing with write-once mail data, where all actions after receiving a message get written somewhere outside of where the mail content is stored... including expunges.  This is a step in that direction.

Bill