[ILUG] 2 quick mail questions.
Padraig at AnteFacto.com
Fri Mar 2 11:02:07 GMT 2001
Conor Daly wrote:
> On Thu, Mar 01, 2001 at 02:05:35PM +0000 or so it is rumoured hereabouts,
> Thomas Bridge thought:
>> Having said that - exim, sendmail/procmail and of course qmail all support
>> using Maildir format mailboxes.
>> Its not a bad idea to use Maildir anyway.
> Interestingly, my ILUG mbox type mailbox is currently about 3Mb in size
> with about 879 messages using an average of 3706 bytes per message. Some
> of these would be long messages but more would be short and would be
> significantly less than 3706 bytes. Now, with the default inode size of
> 4096 bytes on an ext2 filesystem, each message in Maildir format will
> take up at least 4096 bytes leading to greater disk useage for maildir
> format. Doesn't matter that much here at home but it could get
> significant on a real mail server...
This is a file system issue, which isn't an issue in reiser
as anything that isn't an integer block size is packed directly
into the reiser structures. This is really cool for small mails
as they wont take any disk blocks at all.
Also this is comming soon to ext2, although Linus said on 22/2/1:
"I'd rather see a whole new filesystem than have ext2 do tail-block
Once you do tail fragments, you might as well do the whole filesystem
over and have it do fancier stuff than just handling sub-blocking.
Another way of saying this: if you go to the complexity of no longer
being a purely block-based filesystem, please go the whole way. Make the
thing be extent-based, and get away from the notion that you have to
allocate blocks one at a time. Make the blocksize something nice and
big, not just 4kB or 8kB or something.
And don't call it ext2."
(I think he's talking about reiser :-))
Definitely comming soon to ext2 is directory indexing. I.E. you can have
millions of mail files (maildir) with no performance degradation. At the
moment Ext2 does each directory access using a simple, linear search
though the entire directory file, resulting in n**2 behaviour to
create/delete n files. The code has already been written and is being
tested. Of course reiser has this already.
So if you want to make a nice big scalable mail server, store the
mails on reiser in maildir format. There is a problem however, reiser
is not 100% stable yet, especially over NFS.
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