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DFS Necessary? RRS feed

  • Question

  • We are a medium sized company of 300 employees in a central office. We have some smaller remote offices but no data is housed there. I just completed a server consolidation of three older win2000 file servers into the remaining larger windows 2003 server in preperation for an upgrade to 2008.

    I have been debating introducing dfs into the environment. As far as I am concerned and having exposure in the past and how it proved to not be worth the trouble at that time...I am thinking we can easily do without it right now. I can for see us retaining a single large centralized file server for our environment for the forseeable future.  Because of this single server structure, lack of numerous additional servers each with different shares and a lack of remote locations in which a necessity for dfs-r for instance (a different technology anyways) I dont really see a need for it right now.

    I have however been contemplating introducing a cluster for our file server. We are housing about 4.5 - 5tb (depending on the week) and being the only server housing this information I am rightly concerned about the spof with this.


    Does anyone have any thoughts or comments on this approach? I can more easily see a justification for upgrading our storage array and adding a second server vs. introducing another server and requiring as much storage space on that box as the data we want to replicate and keep available.

    I am interested to hear other's take on this.
    Monday, June 9, 2008 10:01 PM

Answers

  • Hello Scott,



    There seems to be some confusion around the Distributed File System (DFS) and Windows server clustering.

    First, let's look at the terms for DFS so we start from the same foundation in this discussion.

    • DFS Root - Think of this as the name space or share name. This is the name that you connect to as a client computer. Underneath the root are the many different folders and files that may be on a single server or may be distributed around to multiple servers. There are two types of roots. There are domain based roots and there are server based roots. Clustering only supports server based roots. Since a domain based root can be created on multiple servers, it is more highly available. A server root does not have that capability as it can only be created on a single server.
    • DFS Link - This is a "leaf" type of object that goes under the root. For example, the root (let's call it SalesFiles) may be hosted on ServerA, but ServerB may have a file share space (call it accounting) that is linked under the root. Once linked, you can access the accounting share two ways. 1. You can connect to the UNC path of \\serverB\accounting or 2. You can connect to the DFS at \\SalesFiles\Accounting or even browse from \\SalesFiles and find the leaf object of Accounting underneath it.
    • DFS Replica (also called a target) - This is another root or even possibly a link in another DFS tree. What we can do is we can use the source and target information and build replicas so that certain leaf objects or entire DFS trees can replicate between locations.

    OK, granted this is just some very high level and basic information, but let's get rolling with it. What does this all have to do with clustering?

    Clustering is used to achieve high availability for certain resources. As a business requirement, we may be told to provide solutions that can help us achieve our goals for the company. One of the requirements is to make certain files highly available as they are needed all the time to keep the business running smoothly.

    We can achieve our goal a few different ways:

    1. We can use DFS and replicas to make copies of the file structures that we deem to be extremely important. The problem with using DFS in this manner is that if there is a great deal of change, the replication process may not be efficient enough to keep up. It is not a good idea to use DFS replication in cases where there is constant change. DFS replication works wonderfully where this is little change, i.e. like hosting application source files and drivers.
    2. We can use server clustering and create file share resources hosted in our cluster environment. One of the nice options of using file server clusters is that we can use the cluster to host a server based DFS root. Because the root is held in the cluster, it makes it highly available. Also, any data stored on the file share on the cluster is also highly available. The value of using DFS in this implementation is that the name space and the link are highly available and we can connect to many links around the organization to help build an easy to navigate file server structure while only hosting the most important files on the cluster itself.
    3. We can deploy a domain root and use it to link to a server cluster running a file share resource and use it as a leaf in our domain root DFS. The domain root can be made highly available because it can be built on multiple servers, and the most important of our files can be hosted on the server cluster file share.

    It is important to note that clusters can not host domain roots. They can only host server roots. 



    Also Refer this link below

    http://technet2.microsoft.com/windowsserver/en/library/aa306635-426e-4fbf-b6a9-542d49af03c01033.mspx?mfr=true


    Thanks and hope this helps




    Syed
    Tuesday, June 10, 2008 6:56 AM

All replies

  • Hello Scott,



    There seems to be some confusion around the Distributed File System (DFS) and Windows server clustering.

    First, let's look at the terms for DFS so we start from the same foundation in this discussion.

    • DFS Root - Think of this as the name space or share name. This is the name that you connect to as a client computer. Underneath the root are the many different folders and files that may be on a single server or may be distributed around to multiple servers. There are two types of roots. There are domain based roots and there are server based roots. Clustering only supports server based roots. Since a domain based root can be created on multiple servers, it is more highly available. A server root does not have that capability as it can only be created on a single server.
    • DFS Link - This is a "leaf" type of object that goes under the root. For example, the root (let's call it SalesFiles) may be hosted on ServerA, but ServerB may have a file share space (call it accounting) that is linked under the root. Once linked, you can access the accounting share two ways. 1. You can connect to the UNC path of \\serverB\accounting or 2. You can connect to the DFS at \\SalesFiles\Accounting or even browse from \\SalesFiles and find the leaf object of Accounting underneath it.
    • DFS Replica (also called a target) - This is another root or even possibly a link in another DFS tree. What we can do is we can use the source and target information and build replicas so that certain leaf objects or entire DFS trees can replicate between locations.

    OK, granted this is just some very high level and basic information, but let's get rolling with it. What does this all have to do with clustering?

    Clustering is used to achieve high availability for certain resources. As a business requirement, we may be told to provide solutions that can help us achieve our goals for the company. One of the requirements is to make certain files highly available as they are needed all the time to keep the business running smoothly.

    We can achieve our goal a few different ways:

    1. We can use DFS and replicas to make copies of the file structures that we deem to be extremely important. The problem with using DFS in this manner is that if there is a great deal of change, the replication process may not be efficient enough to keep up. It is not a good idea to use DFS replication in cases where there is constant change. DFS replication works wonderfully where this is little change, i.e. like hosting application source files and drivers.
    2. We can use server clustering and create file share resources hosted in our cluster environment. One of the nice options of using file server clusters is that we can use the cluster to host a server based DFS root. Because the root is held in the cluster, it makes it highly available. Also, any data stored on the file share on the cluster is also highly available. The value of using DFS in this implementation is that the name space and the link are highly available and we can connect to many links around the organization to help build an easy to navigate file server structure while only hosting the most important files on the cluster itself.
    3. We can deploy a domain root and use it to link to a server cluster running a file share resource and use it as a leaf in our domain root DFS. The domain root can be made highly available because it can be built on multiple servers, and the most important of our files can be hosted on the server cluster file share.

    It is important to note that clusters can not host domain roots. They can only host server roots. 



    Also Refer this link below

    http://technet2.microsoft.com/windowsserver/en/library/aa306635-426e-4fbf-b6a9-542d49af03c01033.mspx?mfr=true


    Thanks and hope this helps




    Syed
    Tuesday, June 10, 2008 6:56 AM
  • Thanks. Although I understand t the difference between clustering and DFS you raised a couple points that I was not really aware of or thought through. What I was asking is given the pros and cons of each technology what is the best approach to take to provide the most availability of the shared file resources that each technology will allow within its own limitations. i think you helped answer that.
    • Edited by 121x Tuesday, June 10, 2008 1:27 PM edit
    Tuesday, June 10, 2008 1:25 PM