[ale] Considerations Regarding Dual Power Supplies

[Jim Kinney]

Ditto. Just be sure that the ground on each PS at the server makes a
SOLID connection to a common point on the chassis and that the ground in
the separate power feeds is a common one.

On Mon, 2008-10-06 at 15:53 -0400, Jeff Lightner wrote:
> You should certainly go to two separate PDUs with separate power
> circuits for redundancy.   We do that with all of our servers
> specifically to insure loss of one PDU or circuit doesn't take servers
> down.
> 
> I did see a presentation once on power that talked about the important
> thing being that everything had a common ground.  It seems if both
> circuits go to the same ground (and it is the shortest path) you don't
> have to worry about separate PDUs.
> 
> If the PDUs are daisy chained together they're all on the same circuit
> anyway so there's no benefit to spreading the load between them.  I've
> seen some racks that do things that way (often due to poor planning).
> 
> -----Original Message-----
> From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of
> hbbs at comcast.net
> Sent: Monday, October 06, 2008 3:33 PM
> To: ale at ale.org
> Subject: [ale] Considerations Regarding Dual Power Supplies
> 
> In audio-land, you have to be mindful of not creating ground loops, i.e,
> a closed circuit of what should be ground in which EMI (especially 60Hz
> hum and harmonics) can be induced.  
> 
> Knowing that, does it cause problems to run power cables from a machine
> with two power supplies to two different PDUs in a server rack?  Or, is
> it preferable to connect the two power cables to as close to the same
> point as possible (i.e., two electrically adjacent outlets in the same
> PDU)?  Aren't the ground pins in each of the two power supplies going to
> be connected together inside the machine?  If so, it seems as though
> having the two grounds form a big loop might bring a lot of hash into
> the machine through the ground lines.
> 
> - Jeff
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