Bron Gondwana brong at
Wed Mar 17 21:43:57 EDT 2010

On Wed, Mar 17, 2010 at 09:17:49PM -0300, Diego Ventrice wrote:
> Thanks Mark,
> Thats what I guessed. I suppose these files make use of the .seen and
> .sub files under also, right ?

.seen and .sub files are always in your "configdir" - where the 
mailboxes.db and related things are.

It's actually not quite flexible enough for my liking, and I'm
seriously considering a per-file configuration option that will
allow things like deliver.db and statuscache.db to be configured
on different paths - specifically on tmpfs!  We already symlink
the proc directory out to tmpfs, but that's harder to do with
individual files.

... but that's debate for the future: for now there are basically
three locations of interest:

1) the data path, where emails are stored
2) the (optional) metadata path, where you can choose to locate some
   higher IO rate small files
3) the config directory.

In our experience, the size of (2 + 3) with all cyrus.* files except
squat on meta is about 5% (20/1) of data.  The IO rates around 5/1
meta over data.  That makes it a pretty good tradeoff to split the
meta onto small fast storage.

My rough testing a little while back showed about a 50% split between
2 and 3.  So half the IO is to the config directory (databases +
.seen and quota files) and half is to cyrus.index and cyrus.cache files.

This is on machines with lots of memory, so the majority of "hot" data
is in memory - most of the ongoing IO is writes.


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