The old divvying model will not reserve more resources than the current demand in the resource pool, even if the resource pool is configured with a higher reservation. If there is a spike in VM demand after resource divvying is done, DRS will only react when the next resource divvying happens to allocate the remaining reservation. As a result, VMs might suffer from temporary performance issues until the next time resource divvying happens.
Let us consider an example scenario to illustrate the new resource pool reservation divvying model. In this example, we have a resource pool with a memory reservation of 10 GB. It has four VMs of 4 GB RAM each. The VMs are all using only 25% of their configured RAM size (memory demand is 1 GB for each VM). The Reservation, Limit, Shares settings for the resource pool are as shown in Figure 10.
divvying
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