Re: [Jwebmail-devel] Re: Webmail

[Brett F. <br...@fo...>]

http://asg.web.cmu.edu/cyrus/ag.html.
"The Cyrus IMAP Aggregator allows the data to be distributed among multip=
le
machines but still presents a unified system image to the end user. The
administrators can best distribute the IMAP mailboxes among a murder of I=
MAP
servers for any reason (availablility, performance, storage space etc.).
However, the end user sees what appears to be one large IMAP server as th=
e
mail client sees the union of the mailboxes across all the servers.
Similarly, users can share their folders and those folders are visible to
other users. A user's INBOX folder hierarchy can also exist across multip=
le
machines. "

----- Original Message -----
From: "Sebastian Schaffert" <wa...@wa...>
To: "Boni Bruno" <bo...@ds...>
Cc: <jwe...@li...>
Sent: Thursday, March 27, 2003 2:46 AM
Subject: [Jwebmail-devel] Re: Webmail


Am Die, 2003-03-25 um 03.04 schrieb Boni Bruno:
> Sebastian Schaffert wrote:
> > Am Son, 2003-03-23 um 11.14 schrieb Boni Bruno:
> >
> >>I have a client we need to build a webmail type solution for with 500=
K
> >>users to start.  Do you have any references of webmail supporting thi=
s
kind
> >>of load?
> >
> >
> > Frankly, no.
>
> Looks like we will be the first.  ;)

:-)

> > You can e.g. use a load-balancing Servlet container. In this way you
> > will be able to scale to pretty large numbers of users. Also, you wil=
l
> > definately need some kind of load balancing for your IMAP servers, as
> > WebMail relies heavily on them.
> >
>
> Are there load-balancing servlet containers available or will we have t=
o
> build this ourselves?

Apache JServ was capable of doing it, so perhaps Tomcat also has this
feature. I didn't check that, though.

> Even if I load balance the IMAP servers, I
> still have the problem of having multiple message stores with each IMAP
> server which would not be efficient.

The idea I pursued once was the following:

- Have multiple IMAP servers, distribute client mailboxes evenly on
  these servers
- Use an IMAP-Proxy as the "main connection point". This IMAP proxy has
  access to some sort of database (probably most efficient is a dbm hash
  file stored locally) to decide on which IMAP server the client has his
  mailbox

When we considered a large installation, the main problem was disk
access, not network throughput or processing power. With the above
approach, you have one proxy, which simply acts as "forwarder" and has
almost no disk accesses. The IMAP servers with many disk accesses are
distributed.

> I think it makes more sense to
> have web mail fetch and store mail directly from a fast/big backend
database
> like Oracle - wouldn't you agree?  Taking this approach, what component=
s
> can we still use from webmail and what components would we have to buil=
d?

The most simple approach would be to write a JavaMail driver to access a
backend database. JavaMail provides means to do this, just have a look
at the documentation.:-)

You will also need to write a different authentication plugin for
WebMail, but this is pretty simple (have a look at the other
Authenticator classes).

> >
> > No. Webmail uses the JavaMail API for accessing messages, so a feasib=
le
> > solution will be to write a "driver" for JavaMail and your backend
> > database.
> >
>
> If we do this, do we still need IMAP?

No.

> We can configure the front-end
> SMTP servers to store mail directly to the database and have web mail
> fetch/store mail from the database as well.  This would allow us to
> load balance the smtp servers and webmail servers very easily if user
> authentication and mail storage is kept on the backend.  I think it
> can be done to scale Webmail to 500K - 2M users.  What do you think?

Hmm, I don't know. It also largely depends on the usage behaviour of
your clients...
But probably it is possible.

>
> >
> >>Your support is appreciated.
> >>
> >>-boni
> >
>
>

P.S. Copy goes to developer mailinglist, since I am neither the only
developer nor the most active one.:-)

--
Sebastian

| Dipl.-Inform. Sebastian Schaffert                    LFE Programmier-/
| sch...@in...             Modellierungssprachen
| LMU M=FCnchen - Institut f=FCr Informatik - Zimmer C8 - Tel: 089/2180-9=
781

PGP Key fingerprint =3D
       13 1D 2E 4F 20 3E C9 1F  4C 57 52 87 8A 80 48 4D  F5 E9 97 EC





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