[GTALUG] mbox/Maildir [was: Re: Interesting essay on filesystem consistency]

[Alvin Starr]

On 12/23/2015 08:26 PM, D. Hugh Redelmeier wrote:
> | From: Lennart Sorensen <lsorense at csclub.uwaterloo.ca>
> |
> | On Fri, Dec 18, 2015 at 12:17:41PM -0500, Kevin Cozens wrote:
> | > On 12/14/2015 01:36 PM, Lennart Sorensen wrote:
> | > >Well deleting a message requires deleting a file, not rewriting the
> | > >entire mbox after that message, so Maildir is a good idea.
> | >
> | > My first exposure to Maildir was via Qmail. I thought it was a better way to
> | > handle lots of email than sticking everything in a single file that needs to
> | > keep updated as you read and delete messages. Makes you wonder why someone
> | > thought it was a good idea to just drop all email in to a single file in the
> | > first place.
> |
> | A lot less inodes, and older filesystems didn't like large directories.
>
> I've been using mbox format for almost 40 years.  It seems to work
> fairly well for me.
>
> - performance is OK, even for horribly large mbox files
>
> - (touch wood) I don't remember anything lost due to "too many eggs in
>    one basket"
>
> - "external fragmentation" would seem to be a problem with Maildir:
>    file overhead (including rounding up to a full last block) is
>    probably a significant part of the cost of a mail file.
>
> I'm setting up a new mailserver right now and I'm wondering if I
> should switch.  I'm building a CentOS 7 system to replace a CentOS 5
> one.  Learning about Postfix.  (I once more or less understood sendmail.)
>
> I don't use IMAP (yet?).  Maybe IMAP vs mbox would be a problem.  I
> may set up Dovecot -- does that demand Maildir?
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I don't think the issue is between mbox and maildir as much as between 
pop and imap.

POP typicality works with a single mail file and has concurrency issues 
and was not designed with the idea mail folders.
IMAP on the other hand is a much newer protocol and has support for 
concurrency and directory hierarchies and a plethora of other features.

POP and IMAP do not require single or multiple files as their backing store.

To your point the reliability of mbox.
I never had a failure of mbox files but had lots of problems over the 
years with the windows mbox equivalent and I think that is more telling 
of the mail reader/client than the mailstore format.

I did have problems with mailservers that were tight on space and had a 
few big mbox files because mbox requires 2x the file space for mail 
manipulation and that ran me into problems.

I moved to IMAP for the features It is a more complex protocol but is 
typicaly faster and able to handle more clients than an mbox based 
implementation.

I found that some mail users with windows POP clients would download the 
whole mailbox each time they connected to check mail and  that lead to 
some bandwidth and performance issues.
Pushing them to IMAP solved that problem.


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