Microsoft has implemented a database-as-a-service/platform-as-a-service environment known as Azure SQL Database. In this environment, the hardware and instance configuration is taken care of for you. In this environment, you manage and support the databases. Finally we have a production ready cloud database. When looking at pricing models, you will find DTUs, eDTUs, and DSU, which of these is correct for you?
What are DTUs?
Database Transaction Units are the unit of measure comprised of cpu, memory, and disk I/O that are available to a single Azure SQL database. Azure SQL databases have three service tiers made up of basic, standard, and premium. The basic tier supports 5 DTU and a database up to 2GB. The standard tier supports between 10 and 100 DTUs and a database up to 250GB. The premium tier supports between 125 and 4000 DTUs and a database up to 500GB. The top two premium levels P11 and P15 support a database up to 1TB.
What are eDTUs?
Elastic Database Transaction Units are just like DTUs, except these are for elastic pools. An elastic pool is a set of resources that are shared between a set of databases on an Azure SQL server. These are very helpful when you have to support multiple Azure SQL databases or a set of databases with unpredictable workloads. Much like the service tiers with DTUs, eDTUs service tiers are made up of basic, standard, and premium. The basic tier has pools from 100 – 1200 eDTUs, however no one database can consume more than 5 eDTUs. The standard pool also supports 100 – 1200 eDTUs however the databases can consume up to 100 eDTUs. The premium pool supports 125 – 1500 eDTUs. A database can consume up to the pool eDTU limit except for the 1500 eDTU pool. A database can only consume up to 1000 eDTU in that pool.
What are DSUs?
Database Stretch Units are the unit of measure for compute when using SQL Server Stretch Database. When you migrate warm or cold transactional data using Stretch Database, it stores the data in an Azure SQL database. DSU levels range from 100 DSUs up to 6000 DSUs.
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