Hi my name is Chris and I'm a global support engineer for Dell EMC
and today I want to talk about configuring the power subsystem on Dell's PowerEdge platform.
Now the best place to do this, is going to be in the iDRAC web interface. Once you've logged in,
just click on Configuration and then Power Management and you'll come to this screen.
And our first option will be Power Control. This does exactly what it sounds like, you can power
the server on and off, you can send a non-maskable interrupt if you're doing some diagnostic work,
you can tell the operating system to perform a graceful shutdown, before powering the server off
you can also choose to reset the system or do what's called a warm boot. This will reboot
the server but it won't power it off first. And then finally you can power cycle the server or do
what's called a cold boot. This will fully power the server off before bringing it back online.
Next we have the Power Cap Policy. Now this is a licensed feature for iDRAC Enterprise and
Datacenter licenses, so not every iDRAC is going to have this option, but it allows datacenter
admins to set the maximum amount of power that the server can request from its datacenter
and the server will adjust its performance to stay underneath that power cap
at all times. Under bursts of heavy load the power cap can be temporarily exceeded
by the server in order to accommodate that load but it will try to adjust its
performance and get back underneath that power cap as quickly as it can.
And then finally we have Power Configuration. Here we can set our power supply redundancy policy.
Now my server has four power supplies in it, which means I get an extra option. Typically you'll only
see a, b, grid redundant and not redundant options for servers with two power supplies,
but my server also has the PSU redundant option which we'll explain here in a little bit. The
default setting is going to be a, b, grid redundant and this sub divides your power
supplies into two different power grids. Since I have four power supplies, my power grid a is
made up of power supply one and three and power grid b is made up of power supplies 2 and 4.
In this scenario if either power supply in power grid a fails, then we'll fail over
to power grid b and power supplies 2 and 4 will take over as the active power supplies.
PSU redundant like I said, is only an option on servers with four power supplies.
And what this means is, the power supplies are still redundant but they're not broken
down into grids. So if power supply 1 fails, the server doesn't lose access to power supply 3.
It will still continue to contribute to the server's power draw.
And then finally we have not redundant, which again is exactly as it sounds, the power supplies
no longer provide any redundancy but they are able to provide their maximum wattage to the server.
As an example, if I have an R740 with two 500 watt power supplies
in a b grid redundant, the maximum power draw that server could have is 500 watts but if the
power supplies are not redundant then the server can draw up to a maximum of 1000 watts of power.
I don't typically recommend using this setting for day-to-day activity,
but I do use it for troubleshooting and diagnostic purposes. Oftentimes we'll get clients that call
us after having added a raid controller or a couple of NICs to their server and found that
it no longer powers on. If that's the case I'll direct the support representative to come here
into the iDRAC, change the redundancy policy to not redundant and attempt to power on the server.
If the server powers on, that's generally a good indicator that the customer has added
more hardware than a single power supply can manage and that's usually a good indicator that
the client should talk to their sales rep about purchasing a higher capacity power supply like a
700 watt maybe 1000 watt power supply in order to continue operating in a redundant state.
I'll go ahead and put this back to 8 equals redundant and then
the next option here is the hot spare feature.
A hot spare power supply will be put into a low power or hibernating state
by the server, if it's enabled. If the hot spare feature is not enabled then all of the
power supplies in the server will attempt to contribute the same amount of power.
Going back to my R740 example with the two 500 watt power supplies,
if I have a hot spare enabled, then the hot spare power supply will be put in a low power state
while power supply 1 or the active power supply,
supplies all the power needs to that server. So if the server only needs 100 watts of power,
power supply 1 will supply all 100 watts and power supply 2 will
not supply any and will sit in a hibernating state. If the hot spare feature is disabled,
then both, power supply 1 and power supply 2 will each contribute 50 watts of power to the server.
if we have the hot spare feature enabled, we will need to select a primary PSU.
In my case, since I'm a grid redundant and I've got four power supplies, I'm actually selecting
a primary power grid. So in this instance, by default, it'll be power supplies one and three,
as the primary PSUs. These are the active power supplies, which means these are going to be the
ones supplying all the power to the server while power supplies 2 and 4 remain in a low power state
until they're called upon. If the hot spare feature is disabled then this option is grayed
out and cannot be selected, because all the power supplies are contributing an even amount of power
to the server. And then finally we have power factor correction, it's enabled from the factory
and its job is to increase the efficiency at which the power supplies apply power to the
server and reduce what's called wasted power. For larger datacenters, large amounts of wasted power
can incur penalties and other fees from their power providers and so having this enabled
will help avoid that for them and just be more efficient and a little bit greener.
You can disable this if you need to. The only thing that disabling power factor correction
will do, is that it will draw less power when the server is in an S5 state or a powered off state.
So if you have to have large numbers of servers in a powered off state for an extended period of
time, disabling power factor correction will save a little bit of energy in that state.
Those are all the primary points of configuring the power supply that we have today.
Thank you very much for listening and have a good rest of your day.