Tag: VMware

A common issue is where administrators intend to use resource pools strictly for organization and administration. They did not intend to affect the resource usage of the VMs, so each pool is set with default Shares, Reservation, and Limit for both CPU and RAM. The administrator utilizes the pool for administration purposes, such as to configure permissions and alarms, but the pools are not used to configure resource settings. This results in each pool having the same Shares for CPU and Memory, but if one pool contains twice the number of VMs than another pool, then each VM in the first pool is effectively guaranteed only 50% of the amount of CPU and RAM that is guaranteed to VMs in the second pool.

A common issue is that VMs are placed outside of any resource pools, leaving them at the same level as the highest level of user-created resource pools. For example, an administrator created two VMs named VM-1 and VM-2. One resource pool was named Sales and the other was named Finance, each having Normal Shares, which is equivalent to 4,000 CPU shares. The Limit and Reservation settings of each pool and VMs were left at default values. The administrator was shocked that when under a period of heavy CPU usage, the Sales and Finance VMs appeared to drag excessively, yet VM-1 and VM‑2 continued working normally. Eventually, the problem was traced to the allocation of the CPU Shares. Each VM in the Sales and Finance Pools had obtained a much smaller number of CPU Shares than VM-1 and VM-2.

Resource Pools are often misunderstood, disliked, and untrusted by vSphere Administrators. However, resource pools can be very useful tools for administrators who want to configure resource management without having to individually configure each VM. This leads to the administrator’s desire to explore the proper usage of resource pools.