We are investigating doing similar things using a separate web interface,
however it is probably possible to run for example two imail servers in a
more fault tolerant manner.
The basic idea I had in mind: (I am using though)
Run the imail servers with identical configuration, including domains hosted
in registry.
Use the same SQL database to store the accounts database.
Store the domain data on a network share accessible by the user that IMail
services log on as.
The network share can either be on a normal NT server or a clustered server.
Essentially you're not actually clustering IMail however the IMAP and SMTP
session could be served by any of Imail servers. The WLBS could be used to
provide the load balancing on port 143 for IMAP, port 25 for SMTP. You can
probably get away without have any affinity set on WLBS as well.
That said, this is not what we are looking to do and I have not tested this
at all. This is more of a thought experiment in how I would do it. I can see
the main issues being file locks or concurrent access by the Imail servers
however I think that the file sharing mechanism under NT is probably robust
enough to handle a couple of servers. This would offer failover like a
cluster because if an Imail server disappeared the other could instantly
take over, thanks to WLBS. If it does work this would offer better
scalability than a cluster aware application because you are not leaving a
server as a hot spare as is the case with Cluster service.
One possible down side is that you should have a quick (switched) ethernet
segment between the file share and the Imail servers.
Obviously if people have tried this and I am talking complete rubbish please
let me know.
Cheers
Steve
----- Original Message -----
From: "Andrews, Bryan (CCI-Atlanta)" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, November 30, 1999 9:33 PM
Subject: RE: [IMail Forum] SQL 7.0
> Hmmm... again I was under the impression that peering was the only option
> (currently) for IMAIL. It will queue up messages when splitting the domain
> between multiple boxes if one goes down but the down box must be restored
> before those users can login again (thus not fault tolerance).
>
> If there is something I am missing that WLBS can do for IMAIL I am very
> interested in hearing it. The scenario that we are building involves WLBS
> splitting the web calls (on a third party web interface) accessing IMAIL
> (via IMAP) boxes peered on the backend. I am interested in hearing any
other
> methods as well...
> _______________________________
>
> Bryan Andrews
> Site Administrator - CCI Web
> 404.843.7408
> 404.847.6335 fax
> 404.597.2316 cel
>
> Cox Communications, Inc.
> 1400 Lake Hearn Drive
> Atlanta, GA 30319
> mailto:[EMAIL PROTECTED]
> _______________________________
>
>
> -----Original Message-----
> From: Steven Moore [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, November 30, 1999 3:03 PM
> To: [EMAIL PROTECTED]
> Subject: Re: [IMail Forum] SQL 7.0
>
> Hi,
>
> In answer to both this and your subsequent message about SQL
> 7, we have
> tried to do similar things to you. I have had good
> experiences with the
> external database with SQL 7.0, however as is often
> mentioned on the list,
> the dll supplied by Ipswitch does not check the state of the
> connection once
> open. You can either alter the source code or use an altered
> version created
> by one of the List members (sorry, I don't have the link to
> hand).
>
> Regarding clustering and WLBS, it is very important that any
> web session
> always goes to the same server for the entirety of the
> session, this can be
> done using the Virtual NIC properties setting the 'affinity'
> to 'single'.
> This means that all traffic will goto a certain member of
> the cluster unless
> that node dies.
>
> An additional thought is that I am not sure how you are
> sharing the domain
> data between the two servers, is this using peering? I was
> considering
> storing all the data on a clustered share. This would work
> as long as the
> security permissions for the Imail services matched those
> that could
> reference the share. I was a bit worried about the
> performance hit that this
> would generate. Also it make the solution that bit more
> complex (as if it
> needed to be:)
>
> Unfortunately IMail doesn't currently feature failover
> cluster awareness
> (not a major ommission at the price though).
>
> Hope this helps and I would be interested in other
> experiences in this area.
>
> Steve
>
> Steven Moore
>
> ----- Original Message -----
> From: <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Tuesday, November 30, 1999 6:23 PM
> Subject: [IMail Forum] SQL 7.0
>
>
> >
> >
> >
> > Clustering vs Windows Load Balancing Service
> >
> > Hello,
> >
> > I have built an IMAIL system based on two IMAIL servers in
> a load balanced
> > environment.
> >
> > This arrangement seems to be causing some problems - as
> far as I can work
> out,
> > WLBS balances individual requests from a user, rather than
> the overall
> user
> > session. The result is that the user cannot use the
> system!
> >
> > Has anyone tried using IMAIL server in a Clustered (or any
> other high
> > availability arrangement)?
> >
> > I gather this is not an officially supported option, but
> does anyone have
> any
> > comments?
> >
> > Regards,
> > Mark McSherry
> >
> >
> >
> > The information contained in this E-mail is confidential.
> It may
> > also be legally privileged. It is intended only for the
> stated
> > addressee(s) and access to it by any other person is
> unauthorised.
> > If you are not an addressee, you must not disclose, copy,
> circulate
> > or in any other way use or rely on the information
> contained in this
> > E-mail. Such unauthorised use may be unlawful. If you have
> > received this E-mail in error, please delete it from your
> system.
> >
> > If you require assistance, please contact our IS support
> desk.
> >
> > Thank you.
> >
> > ( E-mail : [EMAIL PROTECTED] )
> >
> >
> > Please visit
> http://www.ipswitch.com/support/mailing-lists.html
> > to be removed from this list.
> >
>
> Please visit
> http://www.ipswitch.com/support/mailing-lists.html
> to be removed from this list.
> Please visit http://www.ipswitch.com/support/mailing-lists.html
> to be removed from this list.
>
Please visit http://www.ipswitch.com/support/mailing-lists.html
to be removed from this list.
