How does CosmosDB distribute throughput when provisioned per database (shared RUs)

2
votes

I have a problem understading how distribution of provisioned throughput works if I set up Cosmos DB to use shared RUs - setting RUs at database level.

I know when set on container (collection) level that throughput is divided between logical partitions e.g. if collection has provisioned throughput 400 RU/s and 10 logical partitions then throughput for each partition is 400/10 = 40 RU/s.

But what about when throughput is set per database? Only documentation I found is https://docs.microsoft.com/en-us/azure/cosmos-db/set-throughput#set-throughput-on-a-database As far as I can tell difference is that physical partitions are not dedicated to single container but can host logical partitions from different containers - does this mean that throughput is divided between all logical partitions of all collections/containers?

For example: I have database with throughput 1000 RU/s and 2 collections, one with 3 logical partitions and second with 7 logical partitions, so is throughput divided 1000 / (3 + 7) = 100 RU/s for each logical partition?

OR Is throughput reserved for all collections/partitions in sum? e.g. there is database with 1000 RU/s and one logical partitions use 800RU/s and other use 200RU/s (no matter what collection) then is it ok as long as they in sum dont exceed 1000 RU/s ?

Maybe question is short - is shared throughput distributed evenly between logical partitions (same as when set on collection level) or is not (somehow different)?

1
azureazure-cosmosdb

1 Answers

0
votes

Thanks for your feedback. If you are configuring the throughput at database level. You cannot guarantee the throughput for each containers in it, unless you configure the throughput for containers as well.

All containers created inside a database with provisioned throughput must be created with a partition key. At any given point of time, the throughput allocated to a container within a database is distributed across all the logical partitions of that container. When you have containers that share provisioned throughput configured on a database, you can't selectively apply the throughput to a specific container or a logical partition.

You can follow this URL for understading the effect of setting throughput at database and containers level. Set throughput on a database and a container

Hope it helps.