File Shares HDD: Read latency different by Access Tier?

Question

File Shares HDD: Read latency different by Access Tier?

Paul Mossman 5

I understand that Read latency is lower for the SSD Media Tier than the HDD Media Tier. And within the HDD Media Tier, data retrieval from the Cool Access Tier incurs additional costs versus the TransactionOptimized and Hot Access Tiers.

But is the read latency different between the TransactionOptimized, Hot, and Cool Access Tiers?

Snehitha Muduganti 5 Reputation points Microsoft External Staff

2026-10-21T18:24:20.2233333+00:00

Hello Paul,

Transaction optimized, Hot, and Cool are pricing and access tiers within the Azure Files HDD media tier. Microsoft does not publish separate read-latency targets or guarantees for these three access tiers.

Therefore, changing an HDD file share between Transaction optimized, Hot, and Cool should not be considered a method of improving read latency. The primary differences are the storage, transaction, and data-retrieval charges based on the expected access pattern.

Actual read latency can still vary depending on factors such as network conditions, request size, concurrency, throttling, and client location. If the workload requires consistently lower latency, the appropriate option is the Azure Files SSD media tier.
Paul Mossman 5 Reputation points

2026-10-22T11:38:12.5133333+00:00

Hi Snehitha,

To confirm my understanding: No, there's no read-latency difference between the TransactionOptimized, Hot, and Cool Access Tiers of the HDD Media Tier. While read-latency has no guarantees and can vary depending on a number of factors, in practice the Access Tier is not one of those factors.

Please let me know if this interpretation is not correct. Thank you.
Alex Burlachenko 26,700 Reputation points MVP Volunteer Moderator

2026-10-23T15:00:20.5033333+00:00

Hi Paul Mossman & thx for join me at Q&A platform,

No, there's no inherent read latency difference between Transaction Optimized, Hot, and Cool access tiers for Azure Files HDD shares. Microsoft confirms that all three access tiers use the same underlying storage hardware. The difference is primarily in pricing, not performance.

Transaction Optimized has higher storage costs but lower transaction charges. Hot provides a balance between the two, while Cool offers lower storage costs with higher transaction charges and additional data retrieval fees.

Importantly, Cool doesn't mean slower access or delayed retrieval. Unlike the Archive tier in Azure Blob Storage, files in an Azure Files Cool share remain online and immediately accessible. There's no rehydration process.

Actual read latency can still vary depending on I/O patterns, concurrent requests, network conditions, and storage account load, but switching between these three access tiers isn't intended to improve or reduce read performance.

If u want to compare actual latency, Azure Monitor provides SuccessServerLatency and SuccessE2ELatency metrics. Those can help distinguish storage-side latency from network and client-side delays.

So I'd choose between Transaction Optimized, Hot, and Cool based on storage consumption, transaction volume, and retrieval costs, not expected read latency. For consistently lower read latency, SSD-backed Azure Files would be the appropriate option.

rgds,

Alex

p.s. if my answer is help - pls mark it as an answer
Paul Mossman 5 Reputation points

2026-10-27T13:24:43.49+00:00

Hi @Alex Burlachenko ,

Thank you, that does answer my question: There's no read latency difference between the access tiers.

Can you cite where Microsoft confirms this? I was not able to find anything.
Alex Burlachenko 26,700 Reputation points MVP Volunteer Moderator

2026-10-27T13:33:10.5333333+00:00

Hi Paul,

Sure, and thanks for asking for the source. Microsoft confirms this in the official Azure Files docs https://learn.microsoft.com/en-us/azure/storage/files/understanding-billing#differences-in-access-tiers

Microsoft explicitly states "All three access tiers use the same storage hardware." It also explains that the main differences are storage and transaction pricing. There's also the https://learn.microsoft.com/en-us/azure/storage/files/understand-performance , which distinguishes performance characteristics between HDD and SSD rather than between Transaction Optimized, Hot, and Cool. One clarification to my original answer: Microsoft doesn't guarantee identical latency for every individual read. More precisely, there's no documented read-latency advantage associated with choosing one of these three HDD access tiers.

So the recommendation remains the same choose the HDD access tier based on cost, not an expected latency improvement.

rgds,

Alex

p.s. if my answer is help - pls mark it as an answer
Paul Mossman 5 Reputation points

2026-11-04T13:21:00.3266667+00:00

Hi @Alex Burlachenko ,

Yes, I read both of those articles when researching this. But I don't interpret "All three access tiers use the same storage hardware" as meaning there's no read latency difference between them. The article goes on to say that the "main" difference is pricing, but not whether read latency is or is not one of the other differences.

Thank you for your replies, but I don't think my question is answered until I see a clear reply or clear documentation from Microsoft.
Eber Daniel Perez 165 Reputation points

2026-11-04T21:15:07.7866667+00:00
Paul, here are the two official statements that together answer this:

Same hardware across HDD access tiers. From "Understand Azure Files billing", Differences in access tiers: "All three access tiers use the same storage hardware. The main difference between these access tiers is their data at-rest storage prices, which are lower in cooler tiers, and the transaction prices, which are higher in the cooler tiers."

Performance is defined by media tier, not access tier. "Understand Azure Files performance" compares SSD and HDD (for example, SSD offers single-digit-millisecond latency for small I/O while HDD doesn't). It publishes no separate latency targets for TransactionOptimized, Hot or Cool. So Microsoft documents no latency difference between access tiers, only between SSD and HDD.

If you want to validate it in your own environment, compare the SuccessServerLatency metric (time spent by the service) against SuccessE2ELatency (which includes client and network) in Azure Monitor. Filter by share or test with two shares in different tiers under the same load.

If you need a formal written commitment beyond the docs, the Feedback button on those pages or a support case would be the channel for that.

Docs:

https://learn.microsoft.com/azure/storage/files/understanding-billing#differences-in-access-tiers

https://learn.microsoft.com/azure/storage/files/understand-performance
Eber Daniel Perez 165 Reputation points

2026-11-04T21:40:20.4866667+00:00

Hi Paul, short answer: no. Microsoft doesn't document any latency difference between Transaction optimized, Hot and Cool.

From the billing docs: "All three access tiers use the same storage hardware." The difference is the price of storage and transactions. Performance depends on the media tier (SSD vs HDD), not the access tier.

If you want to confirm it in your environment, compare SuccessServerLatency and SuccessE2ELatency in Azure Monitor with two shares in different tiers under the same load.

Docs: https://learn.microsoft.com/azure/storage/files/understanding-billing#differences-in-access-tiers https://learn.microsoft.com/azure/storage/files/understand-performance
Paul Mossman 5 Reputation points

2026-11-09T13:20:42.2966667+00:00

Thank you @Alex Burlachenko and @Eber Daniel Perez . I've submitted feedback with this question on the understanding performance page.
Alex Burlachenko 26,700 Reputation points MVP Volunteer Moderator

2026-11-10T08:05:16.3266667+00:00

Hi Paul,

Thanks for following up and submitting the documentation feedback.

I think ur point is valid. Using the same underlying hardware doesn't necessarily prove identical read latency, and the current documentation doesn't explicitly rule out differences in how the HDD access tiers handle read operations.

So the most accurate conclusion is that Microsoft doesn't document any read-latency differences between Transaction Optimized, Hot, and Cool, rather than claiming such differences cannot exist.

Hopefully, the documentation team can clarify this explicitly. It would be useful for anyone making storage architecture decisions based on performance rather than pricing alone.

rgds,

Alex
Praveen Kumar Gudipudi 2,295 Reputation points Microsoft External Staff Moderator

2026-11-11T12:21:32.4+00:00

Hi Paul,

Could you please share the latest update on the issue? If you are still experiencing the issue, kindly let us know.

We would be happy to assist you further.
Paul Mossman 5 Reputation points

2026-11-11T13:31:09.1833333+00:00

@Praveen Kumar Gudipudi - My question remains un-answered.

Your answer

Snehitha Muduganti 5 Reputation points Microsoft External Staff

2026-10-21T18:24:20.2233333+00:00

Hello Paul,

Transaction optimized, Hot, and Cool are pricing and access tiers within the Azure Files HDD media tier. Microsoft does not publish separate read-latency targets or guarantees for these three access tiers.

Therefore, changing an HDD file share between Transaction optimized, Hot, and Cool should not be considered a method of improving read latency. The primary differences are the storage, transaction, and data-retrieval charges based on the expected access pattern.

Actual read latency can still vary depending on factors such as network conditions, request size, concurrency, throttling, and client location. If the workload requires consistently lower latency, the appropriate option is the Azure Files SSD media tier.
Paul Mossman 5 Reputation points

2026-10-22T11:38:12.5133333+00:00

Hi Snehitha,

To confirm my understanding: No, there's no read-latency difference between the TransactionOptimized, Hot, and Cool Access Tiers of the HDD Media Tier. While read-latency has no guarantees and can vary depending on a number of factors, in practice the Access Tier is not one of those factors.

Please let me know if this interpretation is not correct. Thank you.
Alex Burlachenko 26,700 Reputation points MVP Volunteer Moderator

2026-10-23T15:00:20.5033333+00:00

Hi Paul Mossman & thx for join me at Q&A platform,

No, there's no inherent read latency difference between Transaction Optimized, Hot, and Cool access tiers for Azure Files HDD shares. Microsoft confirms that all three access tiers use the same underlying storage hardware. The difference is primarily in pricing, not performance.

Transaction Optimized has higher storage costs but lower transaction charges. Hot provides a balance between the two, while Cool offers lower storage costs with higher transaction charges and additional data retrieval fees.

Importantly, Cool doesn't mean slower access or delayed retrieval. Unlike the Archive tier in Azure Blob Storage, files in an Azure Files Cool share remain online and immediately accessible. There's no rehydration process.

Actual read latency can still vary depending on I/O patterns, concurrent requests, network conditions, and storage account load, but switching between these three access tiers isn't intended to improve or reduce read performance.

If u want to compare actual latency, Azure Monitor provides SuccessServerLatency and SuccessE2ELatency metrics. Those can help distinguish storage-side latency from network and client-side delays.

So I'd choose between Transaction Optimized, Hot, and Cool based on storage consumption, transaction volume, and retrieval costs, not expected read latency. For consistently lower read latency, SSD-backed Azure Files would be the appropriate option.

rgds,

Alex

p.s. if my answer is help - pls mark it as an answer
Paul Mossman 5 Reputation points

2026-10-27T13:24:43.49+00:00

Hi @Alex Burlachenko ,

Thank you, that does answer my question: There's no read latency difference between the access tiers.

Can you cite where Microsoft confirms this? I was not able to find anything.
Alex Burlachenko 26,700 Reputation points MVP Volunteer Moderator

2026-10-27T13:33:10.5333333+00:00

Hi Paul,

Sure, and thanks for asking for the source. Microsoft confirms this in the official Azure Files docs https://learn.microsoft.com/en-us/azure/storage/files/understanding-billing#differences-in-access-tiers

Microsoft explicitly states "All three access tiers use the same storage hardware." It also explains that the main differences are storage and transaction pricing. There's also the https://learn.microsoft.com/en-us/azure/storage/files/understand-performance , which distinguishes performance characteristics between HDD and SSD rather than between Transaction Optimized, Hot, and Cool. One clarification to my original answer: Microsoft doesn't guarantee identical latency for every individual read. More precisely, there's no documented read-latency advantage associated with choosing one of these three HDD access tiers.

So the recommendation remains the same choose the HDD access tier based on cost, not an expected latency improvement.

rgds,

Alex

p.s. if my answer is help - pls mark it as an answer
Paul Mossman 5 Reputation points

2026-11-04T13:21:00.3266667+00:00

Hi @Alex Burlachenko ,

Yes, I read both of those articles when researching this. But I don't interpret "All three access tiers use the same storage hardware" as meaning there's no read latency difference between them. The article goes on to say that the "main" difference is pricing, but not whether read latency is or is not one of the other differences.

Thank you for your replies, but I don't think my question is answered until I see a clear reply or clear documentation from Microsoft.
Eber Daniel Perez 165 Reputation points

2026-11-04T21:15:07.7866667+00:00

Paul, here are the two official statements that together answer this:

Same hardware across HDD access tiers. From "Understand Azure Files billing", Differences in access tiers: "All three access tiers use the same storage hardware. The main difference between these access tiers is their data at-rest storage prices, which are lower in cooler tiers, and the transaction prices, which are higher in the cooler tiers."

Performance is defined by media tier, not access tier. "Understand Azure Files performance" compares SSD and HDD (for example, SSD offers single-digit-millisecond latency for small I/O while HDD doesn't). It publishes no separate latency targets for TransactionOptimized, Hot or Cool. So Microsoft documents no latency difference between access tiers, only between SSD and HDD.

If you want to validate it in your own environment, compare the SuccessServerLatency metric (time spent by the service) against SuccessE2ELatency (which includes client and network) in Azure Monitor. Filter by share or test with two shares in different tiers under the same load.

If you need a formal written commitment beyond the docs, the Feedback button on those pages or a support case would be the channel for that.

Docs:

https://learn.microsoft.com/azure/storage/files/understanding-billing#differences-in-access-tiers

https://learn.microsoft.com/azure/storage/files/understand-performance
Eber Daniel Perez 165 Reputation points

2026-11-04T21:40:20.4866667+00:00

Hi Paul, short answer: no. Microsoft doesn't document any latency difference between Transaction optimized, Hot and Cool.

From the billing docs: "All three access tiers use the same storage hardware." The difference is the price of storage and transactions. Performance depends on the media tier (SSD vs HDD), not the access tier.

If you want to confirm it in your environment, compare SuccessServerLatency and SuccessE2ELatency in Azure Monitor with two shares in different tiers under the same load.

Docs: https://learn.microsoft.com/azure/storage/files/understanding-billing#differences-in-access-tiers https://learn.microsoft.com/azure/storage/files/understand-performance
Paul Mossman 5 Reputation points

2026-11-09T13:20:42.2966667+00:00

Thank you @Alex Burlachenko and @Eber Daniel Perez . I've submitted feedback with this question on the understanding performance page.
Alex Burlachenko 26,700 Reputation points MVP Volunteer Moderator

2026-11-10T08:05:16.3266667+00:00

Hi Paul,

Thanks for following up and submitting the documentation feedback.

I think ur point is valid. Using the same underlying hardware doesn't necessarily prove identical read latency, and the current documentation doesn't explicitly rule out differences in how the HDD access tiers handle read operations.

So the most accurate conclusion is that Microsoft doesn't document any read-latency differences between Transaction Optimized, Hot, and Cool, rather than claiming such differences cannot exist.

Hopefully, the documentation team can clarify this explicitly. It would be useful for anyone making storage architecture decisions based on performance rather than pricing alone.

rgds,

Alex
Praveen Kumar Gudipudi 2,295 Reputation points Microsoft External Staff Moderator

2026-11-11T12:21:32.4+00:00

Hi Paul,

Could you please share the latest update on the issue? If you are still experiencing the issue, kindly let us know.

We would be happy to assist you further.
Paul Mossman 5 Reputation points

2026-11-11T13:31:09.1833333+00:00

@Praveen Kumar Gudipudi - My question remains un-answered.