Part 1: VMware Distributed Power Management Defined
This is Part 1 in a series of posts related to the definition and configuration of VMware Distributed Power Management.
The consolidation of physical servers into Virtual Machines provides significant hardware cost savings and also reduces power consumption throughout the datacenter. VMware Distributed Power Management (DPM) is yet another way to further increase return on investment by continuously analyzing the Virtual Infrastructure and consolidating Virtual Machines onto fewer hosts during times of low utilization. Hosts that are identified by DPM as underutilized are powered off. As capacity requirements increase, DPM powers on additional hosts to handle the load using either Wake-on-LAN (WOL), iLO, or through IPMI calls to a hardware Baseboard Management Controller (BMC).
How do you get started with DPM? First, you need the appropriate licensing that enables Distributed Resource Scheduler (DRS). This means you will need to license VMware vSphere Enterprise or VMware vSphere Enterprise Plus versions of ESX(i). Second, you will need to configure a VMware DRS cluster within vCenter made up of two or more ESX(i) 4.x hosts. Lastly, you will need to enable and configure the DPM feature on the DRS cluster.
The most difficult process to tackle when setting up DPM is selecting and configuring the “wake-up” solution. There are three options, WOL, iLO and IPMI. WOL has been around for many years and works fairly well; though, it is broadcast based. The physical NICs in the ESX(i) host must support WOL and WOL usually needs to be enabled in the BIOS. WOL will not be able to wake-up ESX(i) hosts if the vCenter server is not on the same subnet as the vMotion NICs unless you enable IP directed Broadcasts. WOL works by sending a UDP “magic packet” to all hosts on a subnet with a payload that describes which host should wake-up. All the hosts on the subnet analyze the packet and only the host the command was meant for powers on.
iLO and IPMI can be described together because they are very similar. iLO (Integrated Lights-out) and BMC IPMI (Intelligent Platform Management Interface) are out-of-band devices that allow an administrator or process to interact directly with a server at a hardware level. Because communication with these devices uses unicast they can be located on any subnet within your routed network. iLO devices typically contain more features than most basic IPMI Baseboard Management Controllers (ex. Console Redirection, Virtual Disks, etc.). Most iLO and IPMI solutions are configured in a similar way. At boot, you press a defined key combination to enter the configuration menu. You will need to configure the IP address, subnet, and gateway. Additionally, you may need to specify a VLAN if you are using trunking on your iLO or IPMI network interface. You will also need to define a username and password combination for access to the iLO or IPMI device. vCenter will require this information during the DPM configuration. Also, while you are configuring the device you will want to take note of the MAC address.
An often unknown but important piece of information is that most BMC IPMI devices share a servers internal integrated NICs. Typically, these integrated NICs are also being used by your ESX(i) host for Service Console, vMotion or Virtual Machine traffic. This is a perfectly acceptable configuration except in the following circumstance: On Dell hardware for instance; the BMC (the device which provides the IPMI interface) can only run at 100Mb when the server is powered off. It is common for the integrated NICs to operate at a speed of 1000Mb. It’s also very common for network administrators to force a speed and duplex setting on switch ports for servers at 1000Mb. What happens is that while ESX(i) is up the NICs will run at their designated 1000Mb speed. When the server is powered down the integrated NICs transition to a low power mode of 100Mb. When the switch port is configured for 1000Mb the BMC NICs disconnect and you lose the ability to remotely administer the BMC (i.e. a speed/duplex mismatch occurs). The solution is to enable AUTO/AUTO on the switch ports used by the BMC NICs. The server will negotiate 100Mb when powered off and will negotiate 1000Mb when ESX(i) is up.
In Part 2 of this DPM series we will configure the cluster for DRS and DPM.
