About DR design, How to calculate WAN bandwidth ?

  • 30 May 2014
  • 5 replies
  • 10531 views

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Hi All

I'm a Nutanix partner in Thailand, when I present Nutanix product in DR feature one question alway arise from the customers who seriously interest in this feature.
"How to caculate WAN bandwidth ?", that mean to how effective compression and deduplication of DR feature.

I can not find this information on the Google and Nutanix site.
Please advise me.

TIA.

5 replies

Userlevel 2
Badge +12
Hi --

One way you could break it down is the following:

First replication size (seed replication) = (Total data size - data already existing at target site) * compresstion %
OR
First replication size (seed replication) = (Total data size * expected common data at target) * compresstion %

Where:
  • Total data size = size of the VMs being replicated
  • Data existing at target = data that already exists at the target site and can be deduped and doesn't need to be sent over the wire
  • Expected common data at target = % of data expected to exist at target and can be deduped
  • compression % = compression rate after compression (eg. 5% compression would mean it would be 95% of its original size)
So for example if you had 100GB of data 50GB which already existed at the target you'd replicate 50GB with a 0% compression rate. OR, if you had 100GB of data and expected 50% commonality between the sites you'd replicate 50GB with a 0% compression rate.

Any other subsequent replication (eg. daily, hourly, etc.) replication after would look like the following:

Subsequent replication size = (Change rate for period - data already existing at target site) * compression %
OR
Subsequent replication size = (Change rate for period * expected common data at target) * compression %

Where:
  • Daily change rate for period = amount of data written / changed during n period of time where n is the frequency of replication
  • Data existing at target = data that already exists at the target site and can be deduped and doesn't need to be sent over the wire
  • Expected common data at target = % of data expected to exist at target and can be deduped
  • compression % = compression rate
So if you wanted to replicate every hour and expected 100MB of changed/new data per hour and expected 50% common data at the target, you're replicating 50MB every hour at a 0% compression rate which is equivalent to ~28.4KBps

From there you could calculate the required WAN bandwidth based upon the change rate, replicaiton frequency and expected deduplication rate

Compression ratios will vary greatly based upon the type of data so if you expect 5,10,n% compression you can use that in your calculation.

Hope that helps!
Userlevel 2
Badge +12
I put together a quick Excel workbook where you can insert values and it will provide the data for expected replication traffic, you can download it here: http://1drv.ms/1odk9A2
Badge +1
Hi, Can you please share the excel sheet again or send to venkat@frontier.in
Badge +1
Hi, can you share the link again for the download?
Thanks
Badge +2
Here's the link: https://1drv.ms/x/s!AiZyOKkRLmEkg64fvFxX5qLejo1hEw

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