Read a file from Azure Cool and Cold Tiers.

Question

I have following questions about reading a file from Azure Blob Cool and Cold Tiers.

1. Is it possible to read a file saved in Cool or Cold Tiers? or does it need to bring back to Hot Tier before reading?
2. If a Tier change is required from Cool/Cold to Hot, how long does it take to do it?

Answer 1

@Parmar, Sanjay

1. You can read files directly from the Cool or cold Tier without needing to move them to the Hot Tier.
2. Changing a blob's tier from a cold or cool to hot is instantaneous. Data in the cool tier should be stored for a minimum of 30 days while data in the cold tier should be stored for a minimum of 90 days.

After a blob is created, you can change its tier in either of the following ways:

• By calling the Set Blob Tier operation, either directly or via a lifecycle management policy. Calling Set Blob Tier is typically the best option when you're changing a blob's tier from a warmer tier to a cooler one.

By calling the Copy Blob operation to copy a blob from one tier to another. Calling Copy Blob is recommended for most scenarios where you're rehydrating a blob from the archive tier to an online tier, or moving a blob from cool or cold to hot. By copying a blob, you can avoid the early deletion penalty, if the required storage interval for the source blob hasn't yet elapsed. However, copying a blob results in capacity charges for two blobs, the source blob and the destination blob.

Pricing

Data access charges increase as the tier gets cooler. For data in the cool, cold and archive access tier, you're charged a per-gigabyte data access charge for reads.

Billing impacts when changing a blob's tier

Additional reading:

Set a blob's access tier

Best practices for using blob access tiers

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Answer 2

1. Yes it is possible to read without changing tiers for the Cool as well as cold tier with higher read costs. Cold tier has slightly higher latency for first byte access compared to Hot and Cool tiers.
2. If you decide to change tiers, cool to hot is instant. While cold to hot may take a few hours

You can change tier using the command below:

az storage blob set-tier --account-name <storage-account-name> --container-name <container-name> --name <blob-name> --tier <Hot|Cool>

See: https://learn.microsoft.com/en-us/azure/storage/blobs/access-tiers-overview?source=recommendations#summary-of-access-tier-options

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Regards,

Abiola