Choosing a vCore service tier, compute, memory, storage, and IO resources
Service tiers are differentiated by a range of performance levels, high availability design, fault isolation, types of storage and IO range. The customer must separately configure the required storage and retention period for backups. With the vCore model, single databases and elastic pools are eligible for up to 30 percent savings with the Azure Hybrid Use Benefit for SQL Server.
The following table helps you understand the differences between these two tiers:
|General Purpose||Business Critical|
|Best for||Most business workloads. Offers budget oriented balanced and scalable compute and storage options.||Business applications with high IO requirements. Offers highest resilience to failures using several isolated replicas.|
|Compute||1 to 80 vCore, Gen4 and Gen5||1 to 80 vCore, Gen4 and Gen5|
|Memory||Gen4: 7 GB per core
Gen5: 5.5 GB per core
|Gen4: 7 GB per core
Gen5: 5.5 GB per core
|Storage||Premium remote storage, 5 GB – 4 TB||Local SSD storage, 5 GB – 1 TB|
|IO throughput (approximate)||500 IOPS per vCore with 7000 maximum IOPS||5000 IOPS per core with 200000 maximum IOPS|
|Availability||1 replica, no read-scale||3 replicas, 1 read-scale, zone redundant HA|
|Backups||RA-GRS, 7-35 days (7 days by default)||RA-GRS, 7-35 days (7 days by default)|
If you need less than one vCore of compute capacity, use the DTU-based purchasing model.
See SQL Database FAQ for answers to frequently asked questions.
Consider the following:
- The allocated storage is used by data files (MDF) and log files (LDF) files.
- Each performance level supports a maximum database size, with a default max size of 32 GB.
- When you configure the required database size (size of MDF), 30% of additional storage is automatically added to support LDF
- You can select any database size between 10 GB and the supported maximum
- For Standard storage, increase or decrease size in 10-GB increments
- For Premium storage, increase or decrease size in 250-GB increments
- In the General Purpose service tier,
tempdbuses an attached SSD and this storage cost is included in the vCore price.
- In the Business Critical service tier,
tempdbshares the attached SSD with the MDF and LDF files and the tempDB storage cost is included in the vCore price.
You are charged for the total storage allocated for MDF and LDF.
Under some circumstances, you may need to shrink a database to reclaim unused space. For more information, see Manage file space in Azure SQL Database.
Backups and storage
Storage for database backups is allocated to support the Point in Time Restore (PITR) and Long Term Retention (LTR) capabilities of SQL Database. This storage is allocated separately for each database and billed as two separate per-database charges.
- PITR: Individual database backups are copied to RA-GRS storage are automatically. The storage size increases dynamically as the new backups are created. The storage is used by weekly full backups, daily differential backups, and transaction log backups copied every 5 minutes. The storage consumption depends on the rate of change of the database and the retention period. You can configure a separate retention period for each database between 7 and 35 days. A minimum storage amount equal to 1x of data size is provided at no extra charge. For most databases, this amount is enough to store 7 days of backups.
- LTR: SQL Database offers the option configuring long-term retention of full backups for up to 10 years. If LTR policy is enabled, theses backups are stored in RA-GRS storage automatically, but you can control how often the backups are copied. To meet different compliance requirement, you can select different retention periods for weekly, monthly and/or yearly backups. This configuration will define how much storage will be used for the LTR backups. You can use the LTR pricing calculator to estimate the cost of LTR storage. For more information, see Long-term retention.
Azure Hybrid Use Benefit
In the vCore-based purchasing model, you can exchange your existing licenses for discounted rates on SQL Database using the Azure Hybrid Use Benefit for SQL Server. This Azure benefit allows you to use your on-premises SQL Server licenses to save up to 30% on Azure SQL Database using your on-premises SQL Server licenses with Software Assurance.
Migration of single databases with geo-replication links
Migrating to from DTU-based model to vCore-based model is similar to upgrading or downgrading the geo-replication relationships between Standard and Premium databases. It does not require terminating geo-replication but the user must observe the sequencing rules. When upgrading, you must upgrade the secondary database first, and then upgrade the primary. When downgrading, reverse the order: you must downgrade the primary database first, and then downgrade the secondary.
When using geo-replication between two elastic pools, it is recommended that you designate one pool as the primary and the other – as the secondary. In that case, migrating elastic pools should use the same guidance. However, it is technically it is possible that an elastic pool contains both primary and secondary databases. In this case, to properly migrate you should treat the pool with the higher utilization as “primary” and follow the sequencing rules accordingly.
The following table provides guidance for the specific migration scenarios:
|Current service tier||Target service tier||Migration type||User actions|
|Standard||General purpose||Lateral||Can migrate in any order, but need to ensure an appropriate vCore sizing*|
|Premium||Business Critical||Lateral||Can migrate in any order, but need to ensure appropriate vCore sizing*|
|Standard||Business Critical||Upgrade||Must migrate secondary first|
|Business Critical||Standard||Downgrade||Must migrate primary first|
|Premium||General purpose||Downgrade||Must migrate primary first|
|General purpose||Premium||Upgrade||Must migrate secondary first|
|Business Critical||General purpose||Downgrade||Must migrate primary first|
|General purpose||Business Critical||Upgrade||Must migrate secondary first|
* Each 100 DTU in Standard tier requires at least 1 vCore and each 125 DTU in Premium tier requires at least 1 vCore
Migration of failover groups
Migration of failover groups with multiple databases requires individual migration of the primary and secondary databases. During that process, the same considerations and sequencing rules apply. After the databases are converted to the vCore-based model, the failover group will remain in effect with the same policy settings.
Creation of a geo-replication secondary
You can only create a geo-secondary using the same service tier as the primary. For database with high log generation rate, it is advised that the secondary is created with the same performance level as the primary. If you are creating a geo-secondary in the elastic pool for a single primary database, it is advised that the pool has the
maxVCore setting that matches the primary database performance level. If you are creating a geo-secondary in the elastic pool for a primary in another elastic pool, it is advised that the pools have the same
Using database copy to convert a DTU-based database to a vCore-based database.
You can copy any database with a DTU-based performance level to a database with a vCore-based performance level without restrictions or special sequencing as long as the target performance level supports the maximum database size of the source database. This is because the database copy creates a snapshot of data as of the starting time of the copy operation and does not perform data synchronization between the source and the target.
- For details on specific performance levels and storage size choices available for single database, see SQL Database vCore-based resource limits for single databases
- For details on specific performance levels and storage size choices available for elastic pools see SQL Database vCore-based resource limits for elastic pools.