[Dovecot] dbox vs. mdbox

Timo Sirainen tss at iki.fi
Fri Mar 4 23:19:21 EET 2011

On 4.3.2011, at 23.05, Douglas Mortensen wrote:

> I guess to get more specific, some of the questions I have regarding dbox vs. mdbox are:
> 1. What is the advantage to using multiple files?

mdbox in theory uses less disk I/O for "normal users".

> 2. What is the advantage to using a single sdbox file for each user?

It's simpler. More difficult to get corrupted. Also if in future there exists a filesystem that supports smaller files better, it's then faster than mdbox. Probably unlikely that it will happen anytime soon.

> 3. Is this a binary format, or txt (UTF?)?

dbox headers/metadata is ASCII. The message bodies can of course be anything.

> 4. Are there real-world benchmarks showing measurable differences between maildir, sdbox, mdbox?

Not that I'm aware of. So far everyone I've tried to ask have replaced their whole mail system and their storage, so the before/after numbers can't be compared. I'm very interested in knowing myself too.

> 5. Are sdbox & mdbox equally stable to Maildir? Are they recommended for production systems?

sdbox is so simple that I doubt anyone will find any kind of corruption bugs. mdbox is more complex, but people are using it in production and I haven't heard of any problems recently. Although there have been bugs in how mdbox handles already corrupted files, v2.0.10 had several fixes related to that.

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