Info about disk drives on Basic/Standard Tiers

Question

Hi, I have some small database running on basic tier. I read from documentation that "In the Basic, S0, and S1 service objectives, database files are stored in Azure Standard Storage, which uses hard disk drive (HDD)-based storage media". Anyway, I cannot find informations about disk drives used in Basic/standard elastic pools, hdd or ssd. Where can i find some info? Thanks

Answer 1

This is the information provided by a Microsoft employee on its personal blog:

In looking at the PaaS version of SQL Server, Azure SQL Database, here is the underlying persistent storage that is used for its databases for the various options:

• Singleton: DTU Basic tiers (max 2GB database size) and Standard tiers (max 1TB database size) use blob storage, Premium tier (max 4TB database size) uses a locally attached SSD; vCore General Purpose tier (max 4TB database size) uses premium blob storage, Business Critical tier (max 4TB database size) uses a locally attached SSD
• Managed Instance: General Purpose tier (max 8TB database size) uses premium blob storage (see Storage performance best practices and considerations for Azure SQL DB Managed Instance (General Purpose)), Business Critical tier (max 4TB database size) uses a locally attached SSD
• Hyperscale: Uses standard blob storage (max 100TB database size) but achieves very high performance due to multiple SSD-based caching tiers

Source is here.

Answer 2

Hi Alberto, thank you for your reply. I'm trying to put together your answer with the information from https://learn.microsoft.com/en-us/azure/azure-sql/database/service-tiers-dtu?view=azuresql where I found the reference to hdd on Basic/S0/S1. I would understand that from S2 upwards the drive used are ssd, because differently there wouldn't be a reason to specify the difference. This is why I was asking about elastic pools. Anyway, from your answer I would understand that, for DTU purchase model, all Basic and Standard tiers are based on hdd (standard blob), without differences between S1/S2 etc. (and probably between single database or elastic pools)
It seems a bit contradictory to me. Am I missing something?

Answer 3

Hi Cristian,

The definitive answer should be:

In the Basic, S0, and S1 service objectives, database files are stored in Azure Standard Storage, which uses hard disk drive (HDD)-based storage media

Source: Here.

For the rest of the tiers apply the following:

Both Standard tiers and Premium tiers use a technology called Azure Premium storage, which is eventually backed by SSD. On Standard tiers, the storage is remote from the SQL Server instance processing user requests. On Premium tiers, the SSD storage is local. There are mainly two benefits. First, latency is sub-ms for local reads compared to muli-ms for reads from XIO. Second, SSD supports higher IO throughput. Best regards.

Source: Here.

Estienne Granet was a Microsoft Employee that was my primary connection with Azure SQL team. He is a very trusted source regarding Azure SQL.