Merge pull request #60910 from sjhala-ccs/BZ2024126

BZ#2024126: Added note about concurrent live migrations

Author: sjhala-ccs

virt/install/preparing-cluster-for-virt.adoc

@@ -67,6 +67,18 @@ Live migration has the following requirements:
 * Sufficient RAM and network bandwidth.
 * If the virtual machine uses a host model CPU, the nodes must support the virtual machine's host model CPU.
 
+[NOTE]
+====
+You must ensure that there is enough memory request capacity in the cluster to support node drains that result in live migrations. You can determine the approximate required spare memory by using the following calculation:
+
+----
+Product of (Maximum number of nodes that can drain in parallel) and (Highest total VM memory request allocations across nodes)
+----
+
+The default xref:../../virt/live_migration/virt-live-migration-limits.adoc#virt-live-migration-limits[number of migrations that can run in parallel] in the cluster is 5.
+====
+
+
 // The HA section actually belongs to OpenShift, not Virt
 [id="cluster-high-availability-options_{context}"]
 == Cluster high-availability options