Use of shadow copy to copy only locked files
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#19 Use of shadow copy to copy only locked files
Hello Wangdera,
first of all thank very much for creating Hobocopy, I use it to backup my session on another PC of my network, everything works fine.
My request is that if a file is not locked is it possible to copy it without using volume shadow copy ? I think it can accelerate the process and minimize disk usage, isn't it ?
Thank you
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Actually, as far as I know, it's not possible to copy a file that is locked against read access...because you need to read it. That's why I had to use the volume shadow copy service.
I agree it would be faster to not use VSS, but I don't see how to do that.
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Hello Candera,
thank you for your answer. What I meant in my request was that I thought it was perhaps better to first try to copy each file without VSS, and use VSS ONLY if the file is locked.
Do you think it is possible ?
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Hmm. It's a bit more complicated that that, unfortunately. One of the things that VSS does is to notify VSS-aware software on the machine such as SQL Server that a backup is about to take place. That gives these programs a chance to write their state to disk in a consistent way (e.g. no unflushed writes). A regular copy doesn't allow for that, which would mean that a hobocopy copy might or might not provide consistent state depending on whether one file in the backup set was locked...and it might be some other file entirely.
I realize that there's some overhead to create the shadow copy, but I think that's just the price for being able to create consistent copies of locked files. And I haven't found that the snapshot takes too long to generate - less than a minute on my machine. Not super fast, but not horrendously slow, either.
On the disk usage question, there actually shouldn't be much impact at all. A shadow copy only copies data that has changed since the snapshot. So conceivably the snapshot takes up *no* additional disk space, if no writes are performed on the volume before hobocopy exits. Certainly shadow copying (e.g.) 10GB of data doesn't require 10GB of extra space.
So I think I'm going to leave this RFE closed - I just don't see a good way to do what you're asking. Thanks for taking the time to make the request though, as feedback is always appreciated!
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Ok, ok, thank you to take care about my remarks. I now better understand the functioning of VSS. Knowing that I agree totally with you, the request I've made has no sense, you can forgot it.
Thanks a lot for taking time to respond to my requests.