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About Deduplication in netbackup

Created: 02 Jul 2014 • Updated: 15 Jul 2014 | 5 comments
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We have planned to keep our monthly and yearly backups in to disk. Planning to use netbackup MSDP. Our current backup size is 10TB. Every month full bakcup and 1year retention. My question is first time it will be 10TB and second month will it take dedupe data and keep it for 12months or it will take entire 10TB plus additional changes (say example 200GB changes as every month)10.2TB and keep it for 12 months.If its 10.2 tb means means my total space will be10.2 * 12 = 122.4TB.

Thanks in Advance.

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Riaan.Badenhorst's picture


The first time it will take the full size but you usually get a compression factor on that. So it might become 8.5TB. Then for an subsequent backups you'll only store the amount of deduplicated data, in other words what has changed. You'll see that in the NetBackup activity monitor as a factor of 95% dedupe, which means 5% was stored. So in the end it would probably come close 12/13TB.


Riaan Badenhorst

ITs easy :)

Shil's picture

Hi Riaan,

Thanks a lot for your reply and clear answer.

12/13TB means it will be the year end over all data growth staorage sapce. If I will take my year end backup as new policy will it take the 3TB (13TB -10TB = 3TB ) and keep it as per my reteniton policy?

Marianne's picture

Best to contact your Symantec reseller. 

They have a dedupe calculator where you provide input such as data type (Exchange, SQL, Oracle,VMware, File, etc) size of each data type and retention levels for daily,weekly, monthly, etc, daily change rate and % growth.

Dedupe rates vary greatly depending on data type and change rate.

Based on this info, they will work out what size dedupe pool you will need for year 1, year 2, year 3.
The calculator also allow to 'play' with retention figures - e.g. keep on dedupe disk for short periods, like 2 months, (assuming tape will be used for long-term retention).
So, you can ask for different figures, e.g. 2 month, 6 month, 1 year retention.

Without this kind of info, any kind of estimate is mainly guess work.

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Riaan.Badenhorst's picture


Any subsequently backups would only take up a % of space, it doesn't matter if its daily, weekly, or yearly. It is the exactly the same if you put your daily backups on the appliance (mon, tue, wed, thu, fri, sat) and keep it for 2 weeks (which is 12 copies) as if you take a monthly and keep it for 12 months. You just count the copies on the appliance.

My example here is just for illustration. Contact your local Symantec partner, as Marianne said, to do a calculation for you. Different data types get different compression rates, e.g. virtual machine are usually get high dedupe ratio, sharepoint on the otherhand doesnt.


Riaan Badenhorst

ITs easy :)

Jim-90's picture

Most Dedupe engines do not like:

  • Data that is encrypted (renders the dedupe inefficient because the data is more unique)
  • Date that is compressed (multi media data including voice and video surveillance, same reason as previous)
  • Squillions of tiny files. (renders the dedupe inefficient)
  • Keeping data for short periods of time. (the longer you store the data the more efficient they become)