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| Virtual copy vs physical copy https://3parug.com/viewtopic.php?f=18&t=1107 |
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| Author: | sanjac [ Wed Dec 20, 2017 9:10 am ] |
| Post subject: | Re: Virtual copy vs physical copy |
http://virtualcloudzz.blogspot.ba/2015/ ... ained.html Second sentence in article: "As part of virtal copy process, ... wich freezes the baze volume and vrites all new data to other disk (virtual copy disk)." Is this true?is data contionued to be written on base VV to?? |
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| Author: | MammaGutt [ Wed Dec 20, 2017 10:03 am ] |
| Post subject: | Re: Virtual copy vs physical copy |
To my understanding a virtual copy is just a snapshot. When you create a virtual copy, you will continue to write to the base volume while doing CoW (Copy-on-Write) to the virtual copy (snapshot) for all changes. |
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| Author: | JohnMH [ Wed Dec 20, 2017 10:50 am ] |
| Post subject: | Re: Virtual copy vs physical copy |
Absolutely it's just a snapshot. When you initiate the snap, writes to the base (source) volume are momentarily held in cache until the snapshot metadata copy is complete. Once completed any writes intended for the base volume will continue to be written back down to the base volume. If these writes happen to overwrite already referenced blocks in the snapshot. The original block will either be copied or the metadata redirected (depends on volume type) from the base volume to the snapshot before the refererenced block in the base volume is allowed to be updated. In that way the point in time state of the snapshot is preserved whilst the base volume continues to update. |
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