[Kde-pim] [kdepim-users] Seperate 'sets' of mail boxes

Peter777 peter777 at users.sourceforge.net
Wed Nov 19 12:25:36 GMT 2008

Hi Anne,

On Wednesday 19 November 2008 22:30:49 you wrote:
> On Wednesday 19 November 2008 10:19:18 Peter777 wrote:
> > Pegasus uses mbox, and I've noticed that maildir format in KMail keeps a
> > file for every email message. How slow is very slow ?  I guess it depends
> > on the number of emails in the one file (mbox) and the total size of the
> > folder (one Pegasus .PMM file is over 14Mb ), and also the computer
> > (grunt).
> Put it this way - I wouldn't want to use it.  I changed from mbox a long
> time ago, when my folders got up to 3000 messages.

No doubt a lot depends on the size of the mbox, not so much how many emails. 
Consider the 14Mb Pegasus mbox file, it has only 1680 email messages in it, 
whereas one has 4336 emails in it, and only 11Mb.

> The trouble with mbox is that every time a message changes status or is
> deleted, the whole file has to be read in, compacted if something has been
> deleted, then written back to disk.  With large mailboxes the delay is
> noticeable.

That is not how Pegasus does it, it is very quick. If a message changes 
status, only a small part of the file is modified, the entire file does not 
have to be written back, as the status flags always take up the same area on 
disk. If an email is deleted, again, the whole file does not need to be 
compacted and then written back to disk, all that happens is a flag is set. 
For new mails, they are simply appended to the end of the mbox file, and this 
again does not mean the entire file is rewritten to disk, with file reference 
at 'eof', it's easy to just append one email message.

As an example, I just copied a considerable sized email msg to the 14Mb mbox 
file in Pegasus, it took 1 second, .. done. I'm running a P2-350 with only 
256 Mb ram, and have pegasus, Kmail, gedit, firefox, nautilus, 3 terminal 
windows and a firewall running, in addition to all the other services. So it 
seems 'grunt' doesn't matter so much, but how an mbox is maintained.

It seems from what you are saying that mbox under KMail is very slow indeed.
If that is so, possibly the KMail develops can take a look at 
http://community.pmail.com/forums/1/8987/ShowThread.aspx , and contact David 
Harris, there may be some very nice features to be added to KMail (apart from 
mbox performance). Seems there were no takers from Linux though.  :(

> Conversely, maildir handles only the one message at a time and 
> is very fast.

Won't having (possibly) hundreds of thousands of files with maildir (one file 
per email message) put a significant (extra) load on Linux systems ? There is 
abviously , in Linux , the equivalent of a FAT, so keeping track of so many 
files (or a lot less with mbox) must place some overhead on system 



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