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Simultaneous backups? RRS feed

  • Question

  • I'm using 1371 April CTP build.  Is it possible to backup two client PCs (both happen to be WinXP SP2) at the same time?  I was running a backup on Client1 and initiated a manual backup on Client2.  Client2 reported it was waiting on Client1.  Why should it do this?  I would have assumed that all ten permitted clients should be able to backup at the same time.

    cheers,
    Ben
    Wednesday, April 18, 2007 9:07 PM

Answers

  • No, you can only run a single backup at a time. I don't know the specific reason for the limitation, but would speculate that the server component of backup is only capable of dealing with the storage of one client PC worth of backup data at a time. Remember that the cluster is the unit of backup for WHS, and that a great deal of information must undoubtedly be stored in order to chain the clusters together correctly in a backup "set".

    Also, remember that SIS offers a huge improvement in terms of the amount of data backed up, and therefor how long a backup takes.
    Wednesday, April 18, 2007 9:22 PM
    Moderator

All replies

  • No, you can only run a single backup at a time. I don't know the specific reason for the limitation, but would speculate that the server component of backup is only capable of dealing with the storage of one client PC worth of backup data at a time. Remember that the cluster is the unit of backup for WHS, and that a great deal of information must undoubtedly be stored in order to chain the clusters together correctly in a backup "set".

    Also, remember that SIS offers a huge improvement in terms of the amount of data backed up, and therefor how long a backup takes.
    Wednesday, April 18, 2007 9:22 PM
    Moderator
  • Thanks Ken.  
    cheers,
    Ben
    Wednesday, April 18, 2007 9:29 PM
  • Ken, I have a question regarding this issue and dual core processors. I am not extreamly knowlegable, so please take this into consideration when reading this, thanks. lol

     

    My question is this: Would the Server be able to manage such simultaneous backups with a dual core processor? Isn't such a processor suppose to be able to handle multiple actions at the same time? So, if this is true, I would think that, at least, two backups should be able to be processed at one time. Each core backing up and checking the store against duplicates?

     

    If true, this would not work in my case as I am using a Pentuim four. It does have multi-threading, but it is not a real dual core like the newest processors are. However, from what I have read here, many folks have installed dual core processors on their Server machine. So, maybe for them this would be possible.

     

    Thanks, Seree

    Thursday, April 19, 2007 12:28 AM
  • I'm not a Microsoft employee (though maybe they should pay me for all the time I spend here Smile ) so you should take that into consideration.

    Technically, you are right, in that if an application is written in a particular way, it can support multiple simultaneous threads of execution. On a multi-core processor, those threads can execute on different cores, and thus deliver greater performance.

    In this case, however, I suspect that the determining factor is the backup storage itself. The backups are stored as clusters of data in large (4GB) files. For a number of reasons I won't go into, it may well be that the backup application needs exclusive control over those files while a backup is being processed. (As a matter of fact, I would stake money on this being a factor.) In a case like that, it might well be that there is no way for two threads to access the backup store at the same time, for performance or data integrity reasons.

    Does that help you to understand? Anything further would be unwarranted speculation on the internals of the backup mechanism, which I have not tried to take apart and analyze.
    Thursday, April 19, 2007 1:30 AM
    Moderator
  • Since WHS only stores a cluster once, and if another system has an identical cluster, it only adds a pointer record saying that system 2 is also using it.  If simultaneous backups were allowed, this wouldn't be possible, and backups would consume considerably more storage.  I think that the clusters are stored, and a "backup set" is a set of pointers for a specific computer for a given backup.
    Thursday, April 19, 2007 7:22 PM
  • Hi Ken, I did think you were an employee of Microsoft for the exact reason you stated, the amount of time you spend here helping others and how knowledgable you are.   I appreciated all your contributions before, but now I truely am grateful for all you do here! lol

     

    Actually, what you said did help me understand better. It made me realize that even if WHS has a dual core processor, that doesn't mean the backup program has dual core capabilities. This would be simular to stating that simply because I am running a dual core processor, lets say-----Outlook can send off multiple messages simultaneously, which it can't, one has to wait for the other. A dual core processor allows for, lets say, downloading an item, while listening to music and writing a file in word. Each is a seperate process, but as each is a seperate program or capability, they are able to be carried out simultaneously. If I tried to download two files from the Microsoft downloads page here at connect, I would not be able to do so, even with a dual core processor, as it is using the same program.

     

    So, as WHS backup is a single program or process, it can only process one machine at a time. I may be way of course here, but it makes sense to me when I look at it this way. lol

     

    Thanks for responding, I do appreciate it. I enjoy learning and reading posts here, and many other places, teaches me a lot.

     

    Seree

     

    Edit: I am aware some programs can be ran as multiple processes, such as having two instances of a program running at once. I will use the Cammand prompt as an example. So, this is what confuses me. I am OK however with leaving this as it is for now, perhaps sometime in the future as my knowlege grows I will more fully understand such issues.

    Thursday, April 19, 2007 7:53 PM