This update includes the following fix and improvement for Microsoft Exchange Server 2019 Sizing Calculator:
- Fixes the issue that Sizing Calculator only computes CAS CPU cycles if ServerVersion=2013.
- Simplify the calculation to account for simpler worst case scenario assumptions.
The Site Resilient configuration scenario results in loss of data center (removing half of the nodes) or loss of primary data center where activation in secondary data center (SDC) is blocked by cmdlet or due to lack of specifying at least one non-lagged copy in the SDC. For non-Site Resilient configuration, we evaluate a loss of 50% of all DAG nodes in a single data center.
For customers who deploy multiple LAG copies, these assumptions are based upon the DAG remaining online, but do not ensure that all copies of all databases are available. This is not a side effect of this change, but a configuration that the calculator allows an outage of some databases which could already occur. For instance, in an A/A configuration where there is more than one LAG copy configured, some number of databases will be unable to mount in the SDC and result in an outage, depending upon the layout and number of copies deployed. However, all DAG nodes will remain online.
This change ensures that you don't end up with a calculation that results in 0 servers being available when it should not.