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Re: [OT] maildir (was Re: procmail and Large File Support)

On Monday 28 February 2005 14:26, sean finney <seanius@debian.org> wrote:
> i came up with the number by totalling the mailbox sizes of a 3000 user
> mail system, and then dividing by the total number of messages in these
> mailboxes.  this generated a number around 13k average message size.
> i had to do this as part of assessing the feasability of migrating
> to maildir without reformatting the filesystem.

A couple of years ago I did the same thing on a system with over a million 
users and got much the same result.

> > I thought it was "illegal" to modify a message.
> marking a message as read is one example.  moving a message from one
> mailbox to another is another example.  although it's not modifying the
> message itself, it's moving its location, which with a crappy imap
> server can mean re-writing the contents of two mailboxes.

In most jurisdictions it's legal to do almost anything as long as the users 
are informed in advance.

Anyway this list is about solving technical problems not being bothered with 
laws in some strange part of the world.

On Monday 28 February 2005 19:18, Michelle Konzack <linux4michelle@freenet.de> 
> Mailbox is MUCH slower as Maildir, because it must be scaned entierly,
> but with maildir, most you can spead up the searches while scaning
> only the Headers.

Of course this only applies if there are a significant number of messages 
larger than the file system block size (usually 4K).  If you have a maildir 
in which every message is less than 4K in size you may find that scanning it 
is slower than scanning an mbox with the same data.  The kernel can do 
read-ahead for a large file to improve performance.  Also an application can 
do read-ahead (calling setbuf() with a large buffer would be one way to do 

Usually there are a significant number of messages >4K so this is the case.  
Also Maildir wins on all modifications to the mail store other than adding 
new messages.

Another noteworthy thing about Maildir is that when an application messes up 
it will probably only trash one message.  I use Maildir for my Kmail local 
storage for this reason, I've had problems in the past with Kmail crashing 
and corrupting mbox storage.

http://www.coker.com.au/selinux/   My NSA Security Enhanced Linux packages
http://www.coker.com.au/bonnie++/  Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/    Postal SMTP/POP benchmark
http://www.coker.com.au/~russell/  My home page

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