On 9.2.2011, at 9.21, Javier Miguel Rodríguez wrote: > That is a "tricky" question to ask. It depends on usage, I think the > following: > > > - LDA delivery: load is a bit lower (on disk) in Maildir vs mdbox: in both > cases the message has to be written, indexes are updated, in Maildir indexes > are in ram, so lower "disk" load in this case > > - POP3 access: the same as the previous post > > - IMAP access: this is tricky. In mdbox a /"delete message"/ command only > lowers the refcount, indexes are updated and in the night a cron job runs > doveadm purge. In Maildir, you really delete the message when MUA/webmail > /"compacts"/ the folder, and indexes are updated. I think that mdbox has a > /"delayed IO" /in this case, and has less load on disk on "production hours". > Am I missing anything?
Yes, in theory those are right. I'm interested in finding out some real numbers :) > The stats in the SAN after the change maildir->mdbox do not help, we have > zlib enabled in lda & imap with mdbox, so our # of real IOPs is lower than > Maildir (we did not have zlib enabled) I wonder how large a write can be before it is split to two iops.. With NFS probably smaller I'd guess. Still, I would have thought that even if zlib writes only half as much, the disk iops difference wouldn't be nearly as much.
