The cost for Azure MySQL Flexible Server Backup retention period

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The cost for Azure MySQL Flexible Server Backup retention period

MOTECH M0525 20

The default backup retention period for MySQL Flexible Server is 7 days. Does it use differential backups, incremental snapshots, or full backups every day?

For example, if I have 300 GB of MySQL storage space, only 240 GB is used, and the daily data increment is 2 GB. How is the space required for 7 days of backup retention calculated? Is it 240 GB x 7 days, or 240 GB + (2 GB x 7 days)?

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Answer 1

Kalyani Kondavaradala 4,600 Microsoft External Staff Moderator

Hi @MOTECH M0525,

Thanks for posting your query on Microsoft Q&A!

Yes, you are correct the default backup retention period is 7 days for MySQL Flexible server.

if you have provisioned a server with 250 GB of storage, you have 250 GB of storage available for server backups at no additional charge. If the daily backup usage is 25GB, then you can have up to 10 days of free backup storage. Storage consumed for backups more than 250 GB is charged as per the pricing model.

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Please refer the below Microsoft document for more details:

https://docs.azure.cn/en-us/mysql/flexible-server/concepts-backup-restore

Please let us know if you have further queries on this.

Hopes this information helps you, if it is please Upvote and Accept Answer so that it will help other community members reading this thread.

Thanks,

Kalyani

MOTECH M0525 20 Reputation points

2025-08-19T07:17:57.79+00:00

I have read this document, but it does not explain my problem.
Kalyani Kondavaradala 4,600 Reputation points Microsoft External Staff Moderator

2025-08-19T07:46:48.6033333+00:00
MOTECH M0525 May I confirm if I’ve understood your query correctly? You’d like to know how the backup storage consumption is calculated. Below is the explanation

Backup type:

One full snapshot backup is taken (once per day).

Transaction log backups are taken frequently (every 5 minutes).

The backups are storage snapshots at the underlying storage layer.

These are differential/incremental in nature, not seven separate full copies.

Retention:

By default, retention is 7 days (configurable up to 35).

The service maintains the chain of one full + incremental backups for the retention period.

That means it does not store 7× full database size.

Billing:

You get free backup storage equal to 100% of your provisioned server storage (so in your case, 300 GB free).

Any backup storage above 300 GB is billable.

Backup storage consumed depends on:

One copy of your database size (used space)

Plus the daily incremental changes retained across the retention period.

Calculation:

Base backup (full) = ~240 GB

Incremental changes for 7 days = 2 GB × 7 = 14 GB

Total backup storage ≈ 240 GB + 14 GB = 254 GB

This fits within the free 300 GB backup quota, so no extra charge in this scenario.

Thanks!
MOTECH M0525 20 Reputation points

2025-08-20T00:49:33.1833333+00:00

Thanks Kalyani Kondavaradala. But your answer is different from Adharsh Santhanam's answer, I don't know who is correct?
Kalyani Kondavaradala 4,600 Reputation points Microsoft External Staff Moderator

2025-08-20T06:49:15.9133333+00:00
Hi MOTECH M0525,

I understand your confusion; here is the information verified by Microsoft.

Azure MySQL Flexible Server performs snapshot-based backups, meaning it takes one full snapshot backup daily, along with transaction log backups every five minutes. These snapshots are actually stored in a way that combines full backups with incremental changes, so they don’t store separate copies for each of the 7 days.

Here’s how the calculation works for your scenario:

Base Backup Size: You mentioned that your server shows approximately 240 GB of used storage.

Incremental Changes: You indicated that your daily incremental changes amount to 2 GB.

To calculate the backup storage consumed over 7 days, you would do the following:

Base Backup (full): 240 GB (this is stored once)

Incremental Changes: 2 GB/day × 7 days = 14 GB (this is the total for the 7-day period)

Total Backup Storage Calculation:

Total = 240 GB (base backup) + 14 GB (incremental changes) = 254 GB

Adharsh Santhanam I value your expertise and the effort you've put into this. Just to be safe, would you mind revisiting the details briefly? I want to make sure we’re fully aligned before sharing it externally.

Please let us know if you have further queries on this MOTECH M0525.

Hopes this information helps you, if it is please Upvote and Accept Answer so that it will help other community members reading this thread.

Thanks!

Kalyani

Answer 2

Adharsh Santhanam 7,885 Volunteer Moderator

Hello MOTECH M0525, Azure MySQL Flexible Server uses snapshot-based backups which are stored in locally redundant storage by default. This comprises of daily full snapshot backups of the data files + transaction log backups every 5 minutes.

Extending this discussion to your specific, let's say your daily snapshot is 240 GB and you retain for 7 days, then, your snapshot storage is 240*7 = 1680 GB

Now, you need to add the transaction log backup (let's say 1 GB) for the same 7 days period to this 1680 GB which will result in 1680 + (1*7) = 1687 GB.

Your final backup storage cost is overage beyond the provisioned storage. In this case, it'll be 1687-300=1387 GB.

Please do not forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.

MOTECH M0525 20 Reputation points

2025-08-19T07:08:50.7+00:00

Wow! You mean daily full backups, not incremental snapshots.
MOTECH M0525 20 Reputation points

2025-08-20T00:51:37.6666667+00:00

Thanks Adharsh Santhanam. But your answer is different from Kalyani Kondavaradala's answer, I don't know who is correct?

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The cost for Azure MySQL Flexible Server Backup retention period

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