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DFS replication maximum size

Posted on 2011-05-13
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Hi there,

we have a customer who is goin to have a DC (2008 R2 SP2) in site A and site B.

We want to create a DFS names space with repliction to and from both servers. The total size of the data that will be on this DFS will be around 150GB.

Is this possible to have this much data on a DFS in a replication setup between 2 servers. i read somewhere that 64GB was the max?

Also is there a way we can copy the data using USB drive to site B rather than it copying over the WAN?

thanks,

mike
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Question by:Bertling
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Lee W, MVP earned 2000 total points
ID: 35755028
I believe that's 64 GB MAX SINGLE FILE SIZE.  I believe the total share size is recommended to be under 1 TB... but I don't recall specifically (I did some research on this for a client a while back... and I have another client replicating AT LEAST that much between two sites.

Obviously, initial replication can take time and if you have a LOT of changing data you need a fast internet connection at both sites to keep up with it (and keep in mind that UPLOAD is as important as download).
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by:Bertling
ID: 35755138
site A which is the main site that will start the replication has a 100mbt upload which is great.

is here not also a way i can seed it with a USB hard drive and then visiting site B?

also site B DC will not be live for another 2 weeks.

Is it possible to create a DFS share in site A DC then in 2 weeks time join the site B DC to this?

sorry i have never used DFS before...
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by:pwindell
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...and no one is going to say what a horrible idea it is to use a DC as a File Server?,..no wait,....2 DCs as File Servers?
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by:Bertling
ID: 35755219
pwindell, there is no other choice they are a small business.

we also dont want to run hyper V as they will have to purchase 2 new OS licences which they wont justify.

If there is a big issue with this we will have to use a 3rd party tool to replicate the data from site A to site B...
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by:Lee W, MVP
ID: 35755226
Yes.  When you setup a domain based DFS you can (initially) specify only one server as a part of the DFS and NOT configure replication.  When you configure replication later, you specify the "primary" server that is otherwise authoritative - meaning that if the data it has conflicts with the data the second server has, its data is considered correct and the second server's data is overwritten.

(Before you do this, I STRONGLY recommend you setup some tests first.  You need not test over a WAN - create a couple of local servers and in a test domain and setup DFS to test it and see how it works - document it and then follow that documentation to implement on your production systems).
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by:pwindell
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That's fine.  But I think we have the responsibility to make it clear to anyone doing this that it is a bad idea,...if they still want to do that after being told then it's their choice.
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by:Bertling
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thanks lee,

do i need to initally configure a "namespace" in the DFS control panel for the firt primary server?

then when the new server is active then configure it as a replica?

thanks,

mike
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by:pwindell
ID: 35755297
With 2008R2 you also have the aspect of Branch Cache that is kind of a step beyond regular DFS that you should look into.  I don't have any specific details on it but it shouldn't be hard to find material on MS's site about it (white Papers and such).
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by:Bertling
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pwindell, thanks for that please can you advise what the issues could be?
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by:Bertling
ID: 35755309
i see that when i was installing DFS. i will take a look...

if anyone has any info about that it would be great to know.
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by:Lee W, MVP
Lee W, MVP earned 2000 total points
ID: 35755380
Branch Cache is something I've not looked into in great detail.

DFS with LARGE files and large amounts of data can be a beast... DFS-R though does block level replication, so that 50 GB file does NOT replicate in it's entirety if just one bit (literally) is changed... only a small block is replicated.  This DRAMATICALLY cuts down on bandwidth requirements (of course, you still have to get the initial replication done, but once done, it shouldn't be a big deal).

In larger environments where people are potentially working on the same sets of files then this COULD prove to be problematic - if I edit "ClientFile.xls" and the DFS has me working on Server1 and you modify "ClientFile.xls" and the DFS has you working on Server2, then you could get a conflict and the most recent file is the one that wins (the last one saved).  But this is a similar problem even without DFS and in some ways, DFS COULD make this better since the conflicting file would be saved to an alternate location in case it should have been the authoritative file... without DFS, the changes would be lost entirely (or the user MIGHT be forced to save as a different file name as the application used to work with that file MIGHT detect the file is already open - it really depends on the app - an excel file would detect that, but another type of file might not).
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by:Lee W, MVP
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Also, DFS-R is what is used with 2003 R2 and later.  So as long as you are not setting up a 2003 (non-R2) server, you should be using the vastly more efficient form of DFS.
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by:pwindell
ID: 35755391
BranchCache Technical Overview white paper
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=ee07308f-7c53-4c76-9ed9-670bc25a4c9d.

 Windows Server 2008 R2 TDM Whitepaper
http://download.microsoft.com/download/D/8/8/D88E78C2-2C2B-45CF-8A70-E2621477F27E/0936BranchCacheTCS.docx

BranchCache in Windows 7 and Windows Server 2008 R2 Overview
http://technet.microsoft.com/en-us/library/dd755969(WS.10).aspx

pwindell, thanks for that please can you advise what the issues could be?

There is no "grocery list" of evils.   It is just the whole general concept of allowing File sharing and File system Access to "users" on the same machine that also holds the active directory database.  There is even just the simple concepts of users filling up the drive with who-knows-what which can take down the DC because it ran out of drive space.  Then there is the future logistics of replacing/retiring a DC when it is also a File Server,...of the flip of that in replacing a File Server that also happens to be a DC.
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by:pwindell
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The good thing about DFS,...is that a real File Server can be added to the DFS Goup and the DCs moved out of the DFS Group while the DFS Root and Paths remain unchanged,...for when the company decides to "do it right" and use dedicated File Servers.
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by:Bertling
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Leew, so when we install DFS role on the Server 2008 R2 server we are installing the latest "DFS-R" and it is not an update or additon we need to isntall.

Could you point us in the right direction to create an inital share for the single site A server whcih will be later be changed to a replication setup.
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by:Lee W, MVP
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In my opinion, pwindell is not keeping a critical aspect in mind - not every company is a bank or multi-national firm that can afford to perform complete separation of services.  In an IDEAL world, you WANT all services to be on separate servers... this allows for greater security, greater reliability, and greater uptime for everything.  The problem is, most businesses - unless they are large multi-national companies or financial firms - cannot afford $800+ for a Windows license to be JUST a DHCP server plus another $800+ for a Windows license to be JUST a DNS server plus another $800 for a Windows license to be JUST a domain controller plus... you get the idea.

There are certain things you absolutely want to follow for security and stability, but certain other things that have minimal risk.  A DC/File Server is, in my opinion, a minimal risk.  A DC/Remote Desktop Server (RDS/TS) is NOT a minimal risk and is one instance, for example, where (to me) it doesn't matter if you have 5 users or 5000 - you want the RDS to be on it's own Windows Server.  The money you have and the more security and stability you need, the more you can break things down... but to me, it's nitpicking at a high level to say don't make your file server a DC for most businesses.

(Of course, you haven't specified if you are a 10 person company or a 10,000 person company... but I suspect you are much closer to the 10 person company given the demographics of people who would likely be asking this question and the resources a person at a 10,000 would have to already know this).
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by:Bertling
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thanks for that lee, you are right its a small company with only 6 users!

but we want a nice simple way to setup site B as a disaster recovery for their file data and DFS seems the best way to do this. and its included in the extortionate Server 2008 OS license...
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by:Lee W, MVP
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> so when we install DFS role on the Server 2008 R2 server we are installing the latest "DFS-R"
> and it is not an update or additon we need to isntall.

Correct.

> Could you point us in the right direction to create an inital share for the single site A server
> whcih will be later be changed to a replication setup.

I cannot explicitly detail it at this moment... I've set this up at 3 clients over the last 6 months... once twice (when one of the servers failed and we had to rebuild almost from scratch).

What I can suggest is a simple Google search for "SETUP DFS 2008" - this yields videos, links, and other documentation for configuration.  You basically create the DFS and DFS share first.  THEN you create the replication policy once you have at least two servers in the DFS.  This is done through DFS management.

If memory serves, you create the namespace and the share in DFS and point it to a share on the server.  For example, at some clients, we have their desktop and my documents redirected to a DFS share.  Each server has a share for users (hidden with a $ sign):
\\server1\users$
\\server2\users$

Then the domain based DFS share is something like:

\\clientdomain.local\dfs\Users

That \\clientdomain.local\dfs\Users knows that it redirects to either \\server1\users$ or \\server2\users$ (which one is used depends on which server is available first/least busy (in some respects, again if memory serves)).

When you first set this up, if you don't have the second server ready, then the only entry you'll have will be akin to \\server1\users$ and you'll add the other one later - which means \\clientdomain.local\dfs\Users will only point to \\server1\users$ until you add the other server (and then you setup replication).
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by:pwindell
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In my opinion, pwindell is not keeping a critical aspect in mind -

Let's not get carried away with attacks here Lee.  I've rebuilt the systems are several banks and they are just as bad about wanting to cram everything on one box.  It is not about money most of the time (that's just the excuse),...it is usually financial laziness of just not want to spend the money,..."can not" and just simply "do not want to" are two different things and usually "..can not.." is the given excuse when "...don't want to..." is the real truth.

All I am saying is that we,...as IT Experts,...on this site,...have the responsibility to make these dangers clear to the people.  If they still want to do it wrong then that is their choice.  I have since expressed my misgiving about using the DCs as File Server and lived up to the responsibility I think I share in.  Then I have moved on to trying to give the person documentation concerning Branch Cache that he might find useful.



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by:Lee W, MVP
ID: 35755726
pwindell,

I've offered my opinion to comments you made based on my understanding of them and the apparent context.  As you know, it's not always possible to fully and accurately know the context in which a comment is made.  Your comments, in some cases, lacking specific explanation of an understanding of the likely environment prompted me to say what I said.  If you choose to take offense, so be it - but I was not intending to deny your statements were technically accurate.

I cannot speak to your experiences with banks and other organizations.  I have spoken with and seen the operations of some multi-thousand person companies and the attitude at those I've seen is a complete separate and a strong willingness to spend money on some things I can't believe they spend money on (like a guy to come in and rack the server for them).  But when systems are critical AND the loss of productivity would be significant, it absolutely makes sense to separate the services... When you have to reboot your DC, and your DC is your file server, then you're interrupting your users for 12-20 minutes... that means paying everyone (assuming there are no redundancies) to sit on their hands and potentially do nothing.  In a company of 5000 people, this would be insane... if each person made $10 per hour (low), then a simple server reboot costs AT LEAST $1000 + potential lost sales and angry customers... but in a business of 6, it costs MAYBE $72, while a new server could be anywhere between $800 and $4000.  Clearly, the separation of services is not worth it (in most cases - a stock broker may feel differently if, in that 12 minute window a stock tanks or shoots up but they can't do anything because they are down).

I wasn't objecting to your noting the best way(s)... I was objecting to your not acknowledging that the best ways are not necessary the most appropriate ways.
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by:pwindell
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I was objecting to your not acknowledging that the best ways are not necessary the most appropriate ways.

Yep.  We are not going to agree there.  "Best" and "appropriate" are synonymous to me.  I think you are just going to have to leave it be.
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by:Bertling
ID: 35755888
thanks for the info so far the both of you.

Lee,

to confirm we will only need 1 namespace with 1 share betwean 2 2008 R2 servers. So nothing to complicated...

we created a namespace in the DFS manager \\domain.local\Data (we also used the "server 2008 mode"). We can now see this when we do \\domain.local\ which is great.

we can now copy the data to this folder and create a mapped drive on each PC in site A using a logon script.

by the looks of it all we need to do now is deploy server B in site B and add an additional member of the DFS and then configure them as replicas under the "replication" section of DFS?
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by:kevinhsieh
ID: 35756908
For a DFS namespace, you really need to start with \\domain.local\data, which is the DFS root, and then add a DFS folder \\domain.local\data\folder1, which would then point to \\server1\folder1, and eventually add \\server1\folder1 when the second server comes online.

DFS doesn't have global file locking, so you need to worry about the same file being edited on both servers at the same time. You didn't state how the 2nd server is going to be used, so this may or may not be a problem.

There are several DFS namespace and replication hotfixes available that are not part of the service packs or Windows Update, so you don't have them unless you specifically asked Microsoft for them. Grap the ones that apply to your setup. It's not clear if you are Usinf 2008 SP2 or 2008 R2, as there is no 2008 R2 SP2 as Microsoft just recently realeased SP1.

http://List of currently available hotfixes for Distributed File System (DFS) technologies in Windows Server 2008 and in Windows Server 2008 R2
support.microsoft.com/kb/968429
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by:Bertling
ID: 35764070
Thanks for that.

i can confirm that site B will be a disaster recovery location so if site A goes down they can use the PCs there which will be on the domain and still access the data as it was at site A before it went down.

Im not 100% sure if we have configure th pre requsit for DFS as you have  advised.

currently we just have the \\domain.local\data namespace with server A as the only name space server. all data is in this and we have mapped drives to this share. we have not created any folders.

is creating the folders mandatory? all we want to do is add server B as a namespace server so that can then replicate the data?

thanks,
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by:kevinhsieh
ID: 35766951
Have you looked at the DFS documentation? Step by steps directions below. Setup the namespace first, and then the replication. You also need to have AD Sites and Services properly configured.

http://technet.microsoft.com/en-us/library/cc732863(WS.10).aspx
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