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scooke
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Replications always Full size

Post by scooke » Feb 16, 2010 10:46 am

Hi, I'm busy evaluating Backup and replication, but it doesn't seems to be working correctly.
I've done the initial replication and powered on the VM to make sure its working, I then shut it down and ran the job again, but every time I run it, it seems to replicate the entire 20 GB image (just a test machine)
Is there something I haven't enabled or something?
Some notes about my setup

Source - ESX 3.5 Enterprise (We will be upgrading to vSphere 4 this year)
Target - ESX 3.5 evaluation (We will be installing vSphere 4 Essentials Plus)

Thanks
Steven

Gostev
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Re: Replications always Full size

Post by Gostev » Feb 16, 2010 11:01 am

Steven, the behavior you are observing is expected and correct.

Every time you run the job, only changes are replicated. The amount of data transferred during the incremental passes is equal to the VRB (rollback) file size created next to the replica during the replication pass.

However, for fast replication, you do need to upgrade to ESX4. Before vSphere, VMware did not provide any means to track VMDK changes, so 3rd party vendors like us had to implement its own change tracking mechanisms. These mechanisms require that you read whole VMDK from source to determing the changes since last replication pass (via block hashing). Thus the incremental replication time with ESX 3.5 is just slightly faster than full (initial) replication. However WAN traffic wise, incremental replication uses much less bandwidth as it only transfers changed blocks.

Thank you.

scooke
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Re: Replications always Full size

Post by scooke » Feb 16, 2010 11:29 am

That's not a problem, as long as it's only going to transfer the changes, as it is over a slow link.

Thanks
Steven

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