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kermic
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Estimating data change rates for VR

Hi!

Can anyone please come up with ideas on how to measure estimated data change rates when one is planning to implement VR (with / without SRM) for a particular Virtual Machine?

I know VR shows this info once I've set it up for a VM and configured a specific RPO, but can I do it in advance for my VM? Like using the vSCSI filter in "what-if" mode.

Snapshot and monitoring the delta size might be one possible solution however it involves some risks.

Monitoring VM write requests will skew the picture if the same block is overwritten multiple times during RPO.

Anything else? I'm sure this question has popped up in other heads as well Smiley Happy

Thanks in advance!

WBR

Imants

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Smoggy
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no easy way to do this right now. we are looking at tools/options that allow this.

in 5.1 you can use VR without SRM and you can also replicate "locally" and by that I mean you can deploy the VR appliance and select the same site as the target meaning you don't send any data across your WAN. If you deploy and activate VR for a sample of your VM's you can keep the traffic local and then record (via the VM events tabs filter on events with keywords "delta completed") the delta sizes for the transfers being created which are recorded in those events.

that's one way you could do it.

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memaad
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Hi,


I dont understand why you need to monitor data change rate for protected virtual machine using vSPhere Replicate. If  you think of performance hit because of replication ,  then I suggest you to go through this blog which explain  how replication work.


http://blogs.vmware.com/vsphere/2011/10/how-does-vsphere-replication-work.html


http://blogs.vmware.com/vsphere/2012/05/when-creating-a-disaster-recovery-solution-using-site-recove...


Also here is link for  Advanced vSphere Replication Options for Single VM Replication Performance



http://blogs.vmware.com/vsphere/2012/06/increasing-vr-bandwidth.html

Regards

Mohammed

Mohammed | Mark it as helpful or correct if my suggestion is useful.
kermic
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Hi Mohammed,

What I want to do is try to find out the bandwidth requirements BEFORE implementing VR. For that I need to know the VM data change rate at specific RPO(-s).

WBR

Imants

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Smoggy
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no easy way to do this right now. we are looking at tools/options that allow this.

in 5.1 you can use VR without SRM and you can also replicate "locally" and by that I mean you can deploy the VR appliance and select the same site as the target meaning you don't send any data across your WAN. If you deploy and activate VR for a sample of your VM's you can keep the traffic local and then record (via the VM events tabs filter on events with keywords "delta completed") the delta sizes for the transfers being created which are recorded in those events.

that's one way you could do it.

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kermic
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Thanks Smoggy,

This confirmation was what I was looking for.

I'm not an API guy but (and maybe that is why) I'm wondering if anyone could use data protection APIs and Changed Block Tracking to provide statistics about block change rates...

To my understanding the idea is pretty similar for CBT and vSCSI / VR filter - track the changed blocks since some sort of an event. If the backup is done and CBT table is being reset once a day, maybe we can use it in read-only mode between backup windows?

Anyway, those are just assumptions. Would need to get someone who's familiar with vSphere APIs for Data Protection to confirm.

WBR

Imants

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