First off, the website documentation is really good for Dovecot but while reading I was not able to find anything pertaining to inbox hashing for Maildirs. I saw plenty about hashing the directories that the user mailboxes live in but nothing about specifically hashing an individual user's inbox directory itself.
Is there any method for hashing the inbox automatically after say 5,000 messages are stored? Example
$Maildir/in/0/message0
$Maildir/in/0/message1
$Maildir/in/0/message2
.
$Maildir/in/0/message4999
$Maildir/in/1/message5000
$Maildir/in/1/message5001
etc
I am not currently using Dovecot but am interested to know if this is available or does running with 20,000+ messages in a single inbox not affect the performance much? I have looked into other file system tuning techniques such as enabling ext3 dir_index or using ReiserFS (maybe not ReiserFS anymore). There will likely be 15,000 to 20,000 accounts spread out on one or more servers using a 6-drive RAID10 setup. Most accounts are not expected to have high message quantities but there will be lots of concurrent connections via pop and imap (and webmail imap).
Any suggestions or feedback would be appreciated.