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

[David Collier-Brown]

On 23/12/15 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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mbox works well if the person writing the code knows Unix V6 primitives. 
If not, they can fail (;-))
For messages larger than the atomic-write size of the filesystem, mbox 
can have a race condition, as it depends on atomicity of writes to 
end-of-file to append a whole message at a time.

--dave

-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb at spamcop.net           |                      -- Mark Twain

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