[Dovecot] Question about "slow" storage but fast cpus, plenty of ram and dovecot

Timo Sirainen tss at iki.fi
Sun Dec 12 12:11:45 EET 2010

On 12.12.2010, at 9.39, Stan Hoeppner wrote:

> mail_location = maildir:~/Maildir:INDEX=MEMORY
> The ":INDEX=MEMORY" disables writing the index files to disk, and as the
> name implies, I believe, simply keeps indexes in memory.

I think maybe I shoudn't have called it INDEX=MEMORY, but rather more like INDEX=DISABLE.

> "If you really want to, you can also disable the index files completely
> by appending :INDEX=MEMORY."
> My read of that is that indexing isn't disabled completely, merely
> storing the indexes to disk is disables.  The indexes are still built
> and maintained in memory.
> Timo, is that correct?

It's a per-connection in-memory index. Also there is no kind of caching of anything (dovecot.index.cache file, which is where most of Dovecot performance usually comes from).

> I don't know if, or how much, storing them in RAM via :INDEX=MEMORY
> consumes, as compared to using a ramdisk.  The memory consumption may be
> less or it may be more.  Timo should be able to answer this, and give a
> recommendation as to whether this is even a sane thing to do.

I think INDEX=MEMORY performance is going to suck. http://imapwiki.org/Benchmarking explains IMAP performance a bit more. By default Dovecot is the "Dynamically caching server", but with INDEX=MEMORY it becomes "Non-caching server".

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