Load distribution across PSUs on a Dell PowerEdge

Question

What does the current distribution look like on a Dell PowerEdge R630 (or any for that matter) when using 2 power supplies?

I assume it will either draw continually from both, distributing the load, or it will favour one over the other. If the later, how does it decide which and is there a way to tell while it's running which that is?

Context for the question is I have a rack load of R630s all with dual-PSU and I'm wondering if one PDU has the current capacity to feed the rack if the other one goes.

Note: This is different to the previous question How do servers with redundant power supplies balance consumption? as it specifically asks about Dell R630s

Possible duplicate of [How do servers with redundant power supplies balance consumption?](http://serverfault.com/questions/659452/how-do-servers-with-redundant-power-supplies-balance-consumption) — ewwhite, Oct 16 '16 at 17:01
Not quite. They are asking HP specific and I am asking Dell specific. As stated in some of the answers/comments on that question it does vary by model. — SimonJGreen, Oct 16 '16 at 17:10

score 2 · Accepted Answer · answered Oct 16 '16 at 17:20

I've found the specific answer to the distribution question now, so sharing here just in case others want it. According to the R630 Owner's Manual on page 99:

When two identical power supplies are installed, power supply redundancy (1+1 – with redundancy or 2+0 – without redundancy) is configured in system BIOS. In redundant mode, power is supplied to the system equally from both power supplies when Hot Spare is disabled. When Hot Spare is enabled, one of the PSUs will be put into standby when system utilization is low in order to maximize efficiency.

So in an R630, regardless of configuration, both PSUs will draw evenly except under very low utilisation where only one PSU will be used.

score 1 · Answer 2 · edited Apr 13 '17 at 12:14

1

It depends a bit on your server manufacturer and system settings, but check out the details at:

How do servers with redundant power supplies balance consumption?

It sounds like your real question is: how do I size/plan my power circuit?

If you lose a leg of power, assume full power draw on the surviving circuit.

edited Apr 13 '17 at 12:14

Community

1

answered Oct 16 '16 at 17:01

ewwhite

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That question doesn't answer this question. It's close, but this is about Dell, specifically R630s. – SimonJGreen Oct 16 '16 at 17:11
Most servers will run balanced by default. The ideas are the same. – ewwhite Oct 16 '16 at 17:11
Does the R630 run balanced by default? – SimonJGreen Oct 16 '16 at 17:12
@SimonJGreen It depends on your BIOS settings. – ewwhite Oct 16 '16 at 17:15
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@SimonJGreen R630 run unbalanced (PSU1 active ; PSU2 standby) by default (factory settings) – sfk Oct 18 '16 at 19:45

Load distribution across PSUs on a Dell PowerEdge

2 Answers2