Is immutable storage enough or off-prem 3rd copy required?

  • 20 October 2021
  • 8 replies

Userlevel 1
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Good day peeps,


I would like to discuss immutable storage and the need of off-prem 3rd copy :)

Having immutable storage with both primary and secondary copies in on-prem storage is well and good from a perspective of faster restores. But they are still on-prem. So there is connectivity, own DC’s, thus meaning that if I have access - someone else can have access. Would that be a hack at software level or access gained inside the DC physically, or some disasters to our own DC’s.

We could help manage connectivity aspect with air-gapping that CV has described with it’s workflows or scripts, other set back of that is that copy could take few or more hours to finish, depeding on size of the data.. If you are doing such air-gapped copy daily - you are frequently open. If you are doing such copy 1 a week - you are open for long period of time if your data to copy is not small.

From all of the above, 3rd copy seems quite needful?


What would you think the best setup would be for 3rd copy to off-prem cloud?
Have on-prem MA to backup to cloud? Get another MA in cloud for restores?
What would be your preferences? What advantages Commvault’s mettalic cloud has against AWS, Azure, etc?

8 replies

Userlevel 4
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Is there any reason off-site Tape is not being considered?


Userlevel 1
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To much hassle :)

Userlevel 4
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With your offsite backups (ie 3rd location)  - what are your ‘retention patterns’

Do you need to keep ‘End of Month’ backups for 7 Years (ie 12 x 7 ‘lots’ of End of Month)



Userlevel 1
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@YYZ We would like to keep data around 2-3 days old I would suspect, although not fully decided.

We have on -prem primary copies with 60 days retention in 1 DC, 2nd on -prem copy of 60 days in other DC. 3rd copy would be used only for most important data and with much lower retention to avoid bigger data loss in case both primary and secondary copies are not usable.

Userlevel 4
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That's different from Finance, Health and other requirements where - for legal reasons - they need retention that goes back 7 - 25 years.

In your case - If the 3rd location (Off site) backup can be

  1. Less than 90 days of retention
  2. and you wanted copies to be updated every 2-3 days then the following might be useful
  1. Cloud would be a good choice - specifically because you would only need to keep a single ‘Full’ backup in the cloud
    1. (ie If you retain Long term backups in the Cloud - on the slow and low cost Cloud tiers, you likely need a Full backup taken  (and Sealed) every 120-180 days
  2. Dont be ‘too hard on tape’ :neutral_face:
    1. to complement the Cloud, a useful example is a small Library - with a small number of tapes - and you can write to the Tape and then ‘over write’ the Tape on a weekly basis
    2. You can choose to remove some of the tapes - or possibly leave them inside the library
    3. and use a Media agent to control the Tape and have that Windows/Linux media agent go off-line, when the Tape Library is not being used
    4. If you need to pull back 3-4TB, that's going to be ‘significantly’ faster using Tape than the Cloud
Userlevel 1
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Looking into your last point, is there some information available somewhere about the average performance for data to be retrieved from cloud vs tape?

Userlevel 4
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If you go down the lowest cost route with say AWS Deep Glacier (and thats the only level that approaches tape type cost)

The other Levels (Glacier, and above) get very expensive, very quickly (to store your data)


Then Deep Glacier has a 5 to 48 Hour retrieval time (again dependent upon the ‘tier’ used within Deep Glacier.

Retrieval Speeds for the Cloud:

You might get 150Mbps (best to run your own tests)

With Tape your theoretical speed (LTO7) will be in the order of 800Mbps to 2400 Mbps (It varies when performing restore due to multiplexing etc)

Though in all cases, the action of unpacking and restoring data will reduce those limits.


Dont forget - You can pay higher prices for the Cloud and obtain incredible restore times and incredible restore speeds - but it can be a shock

But if you use it (as you mentioned) to put just your critical data - (assume thats just 10% of your current backup data), its often worth it








Dear Team,

   we have one query, one of our customer have 3TB data which is already backed up form commvault backup, Customer change the new storage location and old storage moved to DR site. Now that old storage act as immutable storage,  we need copy all old 3TB data to that old storage.