Exchange 2013 – Memory (RAM) allocation by the store with an example

First, a reminder of the theory:

  • Exchange store is comprised of 3 services:
  • msexchangerepl.exe = Replication Service Process
  • Microsoft.Exchange.Store.Service.exe = Store Service Process (or Controller)
  • Microsoft.Exchange.Store.Worker.exe = Store Worker Process (1 per DB)

•Algorithm will allocate total ESE cache available for all store worker processes based on physical RAM

– ~25% of total memory allocated to ESE cache

•ESE cache allocated to each database (store worker process) based on number of local database copies and MaximumActiveDatabases configuration

– Static amount of ESE cache allocated to passive and active database copies

•Passive database allocates 20% of max ESE cache target used for active database

– Store worker process will only use max cache target when operating as active

•Max cache target computed at service process startup

– Restart service process when adding/removing copies or changing maximum active database configuration



1- Let’s say your server has 64GB RAM

2- Exchange 2013 store will calculate a max cache target

25% x 64GB RAM = 16GB

That means that potentially, Exchange Store can allocate and use 16GB RAM maximum.


That would be if your server is hosting active databases only: as stated above, for passive databases, Exchange will allocate less memory.

See the point 3- below:

3- Say you will host 10 databases on your server.

The Max cache target computed at service process startup (Microsoft.Exchange.Store.Service.exe) will be evenly distributed between each database : 16GB / 10 = 1.6GB.

For databases that are active on this server, Exchange Store will use 1.6GB cache for these databases.

But for the passive ones on this server, it will use only 20% of the 1.6GB that the Store service that is 327.68MB


So for 5 Passive databases and 5 Active databases, the RAM usage for the Store processes will be

( Max allocated cache per DB x nb active DBs ) + 20% x (Max allocated cache per DB x nb of passive DBs)

( 1.6 x 5 ) + 20% x ( 1.6 x 5 ) = 9.6GB

If you activate all 10 databases on this server, then the RAM usage will then just be :

1.6 x 10 = 16GB.


Download the tool that produces the nice graphs and examples above !