DFS: Is this a scenario good for DFS?

[wilsonj]

My scenario:

* I have a fax server solution that I need to make fully redundant.
* Cliets in the fax server solution only look at a set of file
folders.
* I need to the failover to be automatic
* I need the clients only to connect to the primary file folders
unless that server is offline. This because of licensing of the fax
software and because we get charged by the call on our backup PRI.

So this is my design:
DC1:
has DFS root \\domain\corp

DC2:
has replica of DFS root \\domain\corp

Primary FAX Server:
resides at our main network operations center
has DFS link \\domain\corp\fax
which contains client folders \requests - for fax request
\users - storage of users faxes
\system - contains shared address
book, coversheets, and letterhead

Backup FAX server:
resides at our co-location facility
has DFS link \\domain\corp\fax
which contains client folders \requests - for fax request
\users - storage of users faxes
\system - contains shared address
book, coversheets, and letterhead

DFS will be configured not to exclude any file types in replication.
I am expecting 2 GB of data to be stored in the link, but only 100MB
should be changed/accessed regularly.

I've set it up this way in the lab, and it has worked, but we were
only testing with small bits of data and one user.

We have very high bandwidth between physical sites (OC3 or better) so
my intention is configure all physical sites to exist in the same AD
site except the co-lo.

My concerns:
1) That replication will not be reliable
2) Clients will connect to backup DFS link when the Primary is
available
3) The large amount of data in the links will cause a problem.
4) If there is a failover, then returning to the previous state will
be difficult.

I've been reading a lot about DFS on the web and in the news groups.
And it has made me nervous about implementing this -- are there any
thoughts from the world?

Jason

 

[Daniel Billingsley]

See responses inline

My concerns:
1) That replication will not be reliable

Hmmm. I've seen various behaviors leading me to question the reliability,
at least in the Win2k version. Like replication between the two servers
suddenly stopping for no reason and with no errors, but only in one
direction. YMMV.

2) Clients will connect to backup DFS link when the Primary is
available

They never will if the second target is in a different site.

3) The large amount of data in the links will cause a problem.

2GB with only 100MB volatile should be no problem.

4) If there is a failover, then returning to the previous state will
be difficult.

Nah, it will be rather automatic. The primary server will "catch back up"
in the replication when it comes back online. So, it won't be "difficult",
but there will be some caveats. Mainly because of course the original server
will instantly be considered a valid target for the link again but won't
instantly be syncronized with the other server. So, you'd want to make that
target offline until the replication was back in sync, at least.

However, the part of the equation you haven't described is the faxing server
itself. I would think that's where most of your troubles will arise.

 

[Richard Chinn [MSFT]]

I've cross-posted this to microsoft.public.windows.server.dfs_frs.

As you've found from reading the newsgroups, FRS is not well suited for all
environments where file replication is needed. I suggest taking a look at
the FRS Monitoring Help file. At the beginning are a few pages of
information about appropriate and inappropriate uses for FRS. The help file
comes with Ultrasound, or you can download it separately. Go to
http://www.microsoft.com/frs. Follow the link for "FRS Troubleshooting and
Monitoring." Then save the "FRS Monitoring Help File" link to your local
machine to view it.

Your two machine replica could work, but it depends on how your users access
the files. If they're all read-only (i.e. authoring content is tightly
controlled), FRS could be reasonable.

--Richard

Please post FRS related questions to microsoft.public.windows.server.dfs_frs
and prefix the subject line with "FRS:" to make it easier to spot. Note
that FRS is used to replicate SYSVOL on domain controllers and DFS root and
link targets.

For additional FRS resources, please visit http://www.microsoft.com/frs.

This posting is provided "AS IS" with no warranties, and confers no rights.