[Dovecot] Performance of Maildir vs sdbox/mdbox

[Robert Schetterer]

Am 18.01.2012 13:44, schrieb Lee Standen:
> Hi Guys,
> 
>  
> 
> I've been desperately trying to find some comparative performance
> information about the different mailbox formats supported by Dovecot in
> order to make an assessment on which format is right for our environment.
> 
> This is a brand new build, with customer mailboxes to be migrated in over
> the course of 3-4 months.
> 
>  
> 
> Some details on our new environment:
> 
> * Approximately 1.6M+ mailboxes once all legacy systems are combined
> 
> * NetApp FAS6280 storage w/ 120TB usable for mail storage, 1TB of FlashCache
> in each controller
> 
> * All mail storage presented via NFS over 10Gbps Ethernet (Jumbo Frames)

nfs may not be optimal
clusterfilesystem might better, but this is an heavy seperate discussion

> 
> * Postfix will feed new email to Dovecot via LMTP

perfect

> 
> * Dovecot servers have been split based on their role
> 
>   - Dovecot LDA Servers (running LMTP protocol)
> 
>   - Dovecot POP/IMAP servers (running POP/IMAP protocols)
> 
>   - LDA & POP/IMAP servers are segmented into geographically split groups
> (so no server sees every single mailbox)
> 
>   - Nginx proxy used to terminate customer connections, connections are
> redirected to the appropriate geographic servers
> 
> * Apache Lucene indexes will be used to accelerate IMAP search for users
> 

sounds ok
>  
> 
>  
> 
> Our closest current live configuration (Qmail SMTP, Courier IMAP, Maildir)
> has 600K mailboxes and pushes ~ 35,000 NFS operations per second at peak 

wow thats big

> 
>  
> 
> Some of the things I would like to know:
> 
> * Are we likely to see a reduction in IOPS/User by using Maildir alone under
> Dovecot?
> 
> * What kind of IOPS/User reduction could we expect to see under mdbox?

there should be people on the list , knowing this , by migration done

> 
> * If someone can give some technical reasoning behind why mdbox does less
> IOPS than Maildir?

as far i remember mdbox takes 8 mails per file ( i am not using it
currently, so i didnt investigate it ), better wait for more qualified
answer, anyway mdbox seems recommended in your case

from our last plans about 25k mailboxes we decide using mdbox, as far i
remember....

> 
>  
> 
> I understand some of the reasons for the mdbox IOPS question, but I need
> some more information so we can discuss internally and make a decision as to
> whether we're comfortable going with mdbox from day one.  We're very
> familiar with Maidlir, and there's just some uneasiness internally around
> going to a new mail storage format.
> 
>  
> 
> Thanks!
> 
>  
> 
> 
from my personal knowledge io on storage has most influance of
performance, if at last ,all other setup parts are solved optimal

wait a little bit , i guess more matching answers will come up
after all ,you can hire someone, perhaps Timo, if you stuck in something

-- 
Best Regards

MfG Robert Schetterer

Germany/Munich/Bavaria