Have you ever just wanted an IF Function when creating Super Metrics? Good news, there is one!
Leading on from the last post I did on determining the number of VMs which will fit into cluster, I have decided to further expand it with an IF function to take the Host Admission Policy failure to tolerate level into account as well.
Previously we used a flat 20% overhead as that was the company policy, however that reserved way too many resources on larger clusters, and setting it to a flat two host failures
We wanted to set any Cluster Compute Resource with less than 10 hosts, to only allow for a single host failure, but clusters of 10 and above should allow for two host failures.
In vROps terms this requires a Ternary Expression, or as most people know them, an IF Function.
You can use the ternary operator in an expression to run conditional expressions in the same way you would an IF Function.
This is done in the format:
expression_condition ? expression_if_true : expression_if_false.
So for our example we want to take the metric summary|total_number_hosts and check if the number of hosts is less than 10.
This means our expression condition is:
${this, metric=summary|total_number_hosts}<10
as we want to return a “1” for one host failure if this is true, and “2” for two host failures if it’s 10 or more our full expression is:
(${this, metric=summary|total_number_hosts}<10?1:2)
This means our full code is:
floor(min([(((((${this, metric=cpu|corecount_provisioned})-(((${this, metric=cpu|corecount_provisioned})/${this, metric=summary|total_number_hosts}))*(${this, metric=summary|total_number_hosts}<10?1:2))*4)-(${this, metric=cpu|vcpus_allocated_on_all_vms}))/8),(((((${this, metric=mem|host_provisioned})*((${this, metric=mem|host_provisioned}/${this, metric=summary|total_number_hosts})*(${this, metric=summary|total_number_hosts}<10?1:2)))-(${this, metric=mem|memory_allocated_on_all_vms, depth=1}))/1048576)/32),((((${this, metric=diskspace|total_capacity})*0.7-(${this, metric=diskspace|total_provisioned, depth=1}))/1.33)/(500+32))]))