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Azure Combined Tier

  • 23 March 2022
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A customer of ours intends to move their Azure workload to Metallic in the near future.
Because we don't manage the azure side of things for the customer, I assumed that the Azure blob storage was a combined tier based on what was configured in Commvault (screenshot below).

 

The cloud libraries are configured in Commvault to use a Combined Tier of storage where we write metadata to Hot and chunk data to Archive tier. Based on that I’d suggested that a rehydration of data is needed from Archive tier to hot tier to perform an Auxcopy to Metallic or lodge a ticket with Microsoft to have the entire contents of the blob converted to Hot tier so that it can be read by the AuxCopy process. 

 

CV cloud library explorer shows chunks in Archive tier

To learn more about Azure's blob storage configuration, the customer turned to Microsoft. Microsoft confirmed that no data needed to be rehydrated in order to migrate to Metallic because they could only see Azure's hot-tier blob storage configured on that side.

 

Do you think MS simply looked at the blob's default configuration, which is set to Hot tier, and didn't dig deeper to check if it is a combined tier?
Is there a  Azure's Storage Explorer (similar to CV cloud storage explorer) to access subfolders in a blob and verify the access level of certain files?  

What can we expect to see on the Azure side?  Sorry, i am light on Azure skills...

 

 

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Best answer by Yun Qian 23 March 2022, 13:23

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Yes Azure provides a “Microsoft Azure Storage Explorer” that you can list and check all blob’s access tier:

 

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You can download it from https://azure.microsoft.com/en-us/features/storage-explorer/

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 @Yun Qian , thank you for your feedback. I've asked the customer for Azure manager permissions to use the Explorer.

Question, Is it necessary to select a combined storage class when creating an Azure blob or will a single tier suffice (hot/cool) and will Commvault override the tier selected when the cloud library is configured as a combined tier?  If the latter is the case, will the Azure configurations be altered to reflect the combined tier?  (In our case Commvault shows it's Archive Tier, but the Azure Blob shows it as Hot Tier, which isn't what it appears to be) - just trying to understand if I am missing something here. 

 

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Hi Nikramak,

Let’s clarify some concept/terminologies first:

In the context of azure storage, a “file” is a “blob” object which is stored as:

“Storage account” → “Container” → “Blob”.

 

The storage account has a setting “Default Access Tier”, you can set it as “Hot” (default) or “Cool”, please note that “Archive” can not be used as storage account’s default setting, it is for blob object setting only.

 

When you upload a blob object into the storage account, you can specify the access tier of this individual blob object as hot/cool/archive or specify nothing to use the storage account’s “Default Access Tier” value.

 

Now let’s back to our you case here. It seems that your customer created the storage account using default settings, which will leave the “default access tier” as “hot”. But when Commvault write data into this storage account, we will upload every single blob object with different access tier parameters according to its type (metadata or data), every metadata blob will be uploaded as “hot” and every data blob will be uploaded as “archive”.

 

Hope I have explained it clear for you😀

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And..you can just use Azure Portal (https://portal.azure.com) to run a HTML based storage brower to browse blob objects without using storage explorer... 

 

 

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@Yun Qian ,thank you so much for the detailed explanation and screenshots. This cleared up most my confusion. I've a a few final questions and I won't bother you with any more:
- Is there a way to see how much space is used in each tier of Azure storage accounts?
- I understand that the storage account's default tier can be set to hot/cold only, but is there anywhere I can check to see if this storage account has combined tiers?

- So all data chunks reside in the Archive tier and none on the hot tier? 

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Hi Nikramak,

I’d like to give my answer based on my limited Azure knowledge:

- Is there a way to see how much space is used in each tier of Azure storage accounts?

There is a “folder statistic function” in Azure portal but only for the whole folder, not for each tier…Maybe there are some Powershell cmds exist but I don’t know about it…


- I understand that the storage account's default tier can be set to hot/cold only, but is there anywhere I can check to see if this storage account has combined tiers?

There is no concept called “combined tier“ in Azure, so you have to get a list of all blob objects to check their access tier. You can use the “Blob Inventory” feature in Azure Portal, which can generate a list of all blobs including their access tier in a CSV file (automatic run daily). You can refer to MSFT docs to see how to configure Blob Inventory.

 

- So all data chunks reside in the Archive tier and none on the hot tier? 

Yes, since you have chosen the combine tier in Commvault cloud library setup, ALL data chunks will be in Archive tier unless they are recalled due to a restore operation.

 

You can just keep asking, glad to help😀

 

Yun

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Thank you for your comments @Yun Qian and detailed explanations. We were able to confirm the existence of data in the archive tier by using the "Microsoft Azure Storage Explorer." The "Blob Inventory" was also useful.


The customer has decided to keep their current cloud storage and not migrate to Metallic because the cost of bulk retrieval from the Archive tier is prohibitively expensive. They prefer to leave it there to retire.