Can we downgrade the performance tier of a premium SSD from P30 to P20?

Question

I have Premium SSD disk with performance tier P30, I want to understand whether I can downgrade the performance tier to P20?

Answer 1

You can downgrade the performance tier of a Premium SSD from P30 to P20; however, there is a restriction in place. You can only decrease the performance tier 12 hours after the last increase. If you attempt to downgrade within this timeframe, you will receive an error message indicating that the downgrade cannot be performed before 12 hours have passed since the last increase.

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References:

• Scale storage performance
• Change your performance tier without downtime

Answer 2

Hi Vivek,

If the size of the disk is 512 GiB or less, you can downgrade the performance tier from P30 to P20.

Change your performance tier without downtime

https://learn.microsoft.com/en-us/azure/virtual-machines/disks-performance-tiers

Please click Accept Answer and upvote if the above was helpful.

Thanks.

-TP

Answer 3

Hello @vivek khot

Azure does not support directly downgrading a Premium SSD performance tier from P30 to P20 without resizing the disk. Because performance tiers are tied to disk size, the disk must be resized down to 512 GiB to map to P20, or a new P20 disk must be created and data migrated.

Premium SSD performance is directly tied to disk size. Since P30 is a 1 TB disk and P20 is a 512 GB disk, Azure does not allow changing just the tier without resizing. To downgrade, the disk size must match the target tier, or a new disk must be created.

Steps to perform :

1.Resize the disk

You must resize the disk down to 512 GiB to move from P30 to P20.

Important prerequisites (from real cases):

• The disk must be detached from the VM
• Used space must be less than 512 GiB
• VM should be deallocated before resizing OS disks

High‑level steps (Portal):

1. Stop and deallocate the VM (if OS disk)
2. Detach the disk
3. Resize disk to 512 GiB (this automatically maps it to P20)
4. Reattach the disk
5. Start the VM

2.Create a new P20 disk and migrate data

If resizing down is not possible due to data usage:

1. Create a new Premium SSD P20
2. Attach it to the VM
3. Migrate data using AzCopy.
4. Detach the old P30 disk once validated.

Links:
https://learn.microsoft.com/en-us/azure/virtual-machines/disks-types#premium-ssds

https://docs.azure.cn/en-us/virtual-machines/disks-scalability-targets

Thanks,
Manish Deshpande.