[Dovecot] Howto add another disk storage

[J E Lyon]

On 5 Jul 2012, at 08:44, Adrian M wrote:

> Hi Stan,
> I know how to add drives to the storage and how to grow the existing
> filesystem, but such big filesystems are somehow new to mainstream
> linux. Yes, I know some university out there already have pentabytes
> filesystems, but right now stable linux systems have trouble
> formatting ext4 partition over 16T.
> All this is telling me that is safer to have two or tree smaller
> filesystems than a big one. Dovecot has a nice feature for this
> "Directory hashing" http://wiki.dovecot.org/MailLocation/
> 
> What I don't know is a nice way to migrate from a single directory no
> hashing to more than one and hashing.


When I first saw you mention hashing, I misread it as some sort of hash-table approach to large directories that I wasn't aware of, or something . . And now I've read the Dovecot documentation, I see what you're talking about!

Why are you bothered about using the hash, instead of just splitting on the first letter of the existing account name? Is it to more evenly randomise the distribution of accounts?

The advantage of the username "first letter" approach, or returning hardcoded locations from userdb (as per Timo's suggestion), is that you can more readily move the directories manually during a very short period of downtime, I'd have thought?


~ James.