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  • Question

  • I want to implement BranchCache for our remote users in distributed cache mode but have a few questions before I proceed

    I need to know does file versioning work in the same way in distributed cache mode as in hosted cache mode i.e. the client checks the content server at main office for file changes before deciding wether to download from the client hosting the cache?

    Also does Branch Cache play well with DFS, particularly DFS on a Server 2003 environment?

    Anything else I need to consider before I implement?

    Thanks in advance

    • Changed type Miles Zhang Wednesday, January 5, 2011 3:27 AM
    • Edited by jstalley Sunday, January 9, 2011 2:55 PM change required
    Tuesday, January 4, 2011 12:11 PM

Answers

  • Hi,

    Thanks for the post.

    The client will check the content server at main office for file changes before deciding wether to download from the client hosting the cache. Actually, if both the server and the client support BranchCache, and BranchCache has been enabled for the data, the server does not return the requested file. Instead, the server returns a hash of the data. If any of the Distributed Cache peers have the data cached, they return it to the client. The client then validates the data using the hash (which was created using the secret key stored on the server) to verify that it has not been modified.

    Here is the individual advantage of these two methods:

    Hosted cache provides a central location for the cache and the following benefits:

     

    ·         Increased availability With a Hosted Cache, the server can be always on and provide better WAN link utilization. Client computers can hibernate, shut down, and roam without affecting the availability of cached content. With a distributed cache, content stored on these clients would not be available.
    ·         Increased reliability There should be fewer services and applications running on a server hosting a cache. In addition, the service level agreement (SLA) on the server is likely to be better than when the cache is hosted across client computers. This leads to better reliability and turn-around time if there are issues.

    ·         Caching for the entire branch office A Hosted Cache can reduce WAN traffic across the entire branch office, whereas the Distributed Cache model is scoped to a single subnet in the branch office.

    ****************************************

    Distributed cache offers the following benefits:

     

    ·         Easy set up A distributed cache is easy to deploy using Group Policy. A Hosted Cache requires that a server is set up and that a certificate is bound to the Secure Sockets Layer (SSL).
    ·         No server dependency A distributed cache is convenient for branch offices that do not have a server in the office. The cache is distributed across the users’ computers. However, only users who use the same subnet can access the cache.

    In addition, BranchCache can work weill with DFS, however, as you know, BranchCache just complements DFS and ISA caching and BranchCache stores only intranet data (for both HTTP and SMB protocols), and does not store data that is downloaded from the Internet. It supports distribution of files using the SMB protocol only on the read-path (for two-way synchronization over WAN links, consider using DFS Replication).

    Please understand that BranchCache requires clients running Windows 7. Windows Server 2008 R2 is required on content servers located in the datacenter (the targeted share) as well as on servers hosting caches.

    Hope this helps.

    Miles

     

     

     


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    • Marked as answer by jstalley Wednesday, January 5, 2011 1:55 PM
    Wednesday, January 5, 2011 3:26 AM

All replies

  • Firebrand Training:

    Hello.  Yes, BranchCache modes including Distributed and Hosted Cache modes rely on obtaining the same identifiers from the content servers.

    There are no conflicts with running BranchCache and DFSR in combination.  Some data is better accelerated by one than the other.

    Note:  remote office machines need to have a BranchCache capable Win7 or Serer2008R2 SKU:

    ·         Win7 Ultimate and Enterprise SKUs have full HTTP, SMB and BITS integration for BranchCache - as do Windows2008R2 Server SKUs with some limitations outlined here:

    http://technet.microsoft.com/en-us/library/ee307962(WS.10).aspx#BKMK_4

     Thanks, Si.

    Wednesday, January 5, 2011 2:57 AM
  • Hi,

    Thanks for the post.

    The client will check the content server at main office for file changes before deciding wether to download from the client hosting the cache. Actually, if both the server and the client support BranchCache, and BranchCache has been enabled for the data, the server does not return the requested file. Instead, the server returns a hash of the data. If any of the Distributed Cache peers have the data cached, they return it to the client. The client then validates the data using the hash (which was created using the secret key stored on the server) to verify that it has not been modified.

    Here is the individual advantage of these two methods:

    Hosted cache provides a central location for the cache and the following benefits:

     

    ·         Increased availability With a Hosted Cache, the server can be always on and provide better WAN link utilization. Client computers can hibernate, shut down, and roam without affecting the availability of cached content. With a distributed cache, content stored on these clients would not be available.
    ·         Increased reliability There should be fewer services and applications running on a server hosting a cache. In addition, the service level agreement (SLA) on the server is likely to be better than when the cache is hosted across client computers. This leads to better reliability and turn-around time if there are issues.

    ·         Caching for the entire branch office A Hosted Cache can reduce WAN traffic across the entire branch office, whereas the Distributed Cache model is scoped to a single subnet in the branch office.

    ****************************************

    Distributed cache offers the following benefits:

     

    ·         Easy set up A distributed cache is easy to deploy using Group Policy. A Hosted Cache requires that a server is set up and that a certificate is bound to the Secure Sockets Layer (SSL).
    ·         No server dependency A distributed cache is convenient for branch offices that do not have a server in the office. The cache is distributed across the users’ computers. However, only users who use the same subnet can access the cache.

    In addition, BranchCache can work weill with DFS, however, as you know, BranchCache just complements DFS and ISA caching and BranchCache stores only intranet data (for both HTTP and SMB protocols), and does not store data that is downloaded from the Internet. It supports distribution of files using the SMB protocol only on the read-path (for two-way synchronization over WAN links, consider using DFS Replication).

    Please understand that BranchCache requires clients running Windows 7. Windows Server 2008 R2 is required on content servers located in the datacenter (the targeted share) as well as on servers hosting caches.

    Hope this helps.

    Miles

     

     

     


    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.
    • Marked as answer by jstalley Wednesday, January 5, 2011 1:55 PM
    Wednesday, January 5, 2011 3:26 AM
  • Thanks for the posts this has clarified for me a couple more questions if I may:

    Currently if someone opens a file someone else is using the user trying to access this file gets a message similar to "This file is locked for editing by user. Would you like to open read only?"

    With BranchCache in both modes how does it handle the possibility of multiple people trying to edit files?

    Also in hosted cache mode can the SSL cert be a self cert or does it need to be from a root CA imported into the machines Trusted Root Store?

    Wednesday, January 5, 2011 8:53 AM
  • Hi,

    Thanks for the update.

    AFAIK, BranchCache is only available for downloading the files on the remote office instead of editing files.

    The Hosted Cache server must be equipped with a certificate that is trusted by the client computers in the branch offices.

    The certificate must be added to the certificate store under the local computer account. If the certificate is added to the certificate store belonging to an administrator, or another user on the system, you will be unable to link the certificate to BranchCache, and clients will not be able to connect to the Hosted Cache server.

    For more information, you could refer to this article (http://technet.microsoft.com/en-us/library/dd637793(WS.10).aspx)

    Thanks,

    Miles


    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.
    Friday, January 7, 2011 8:39 AM