[PLUG] dual power supplies and a switch of UPS'

[Charles Sliger]

>From: Rich Shepard <rshepard at appl-ecosys.com>
> On Thu, 16 Feb 2006, Charlie Schluting wrote:
> > One point of clarification: most servers will use BOTH power supplies at
> > ones, in theory reducing the load and making each last longer. Only
really
> > old braindead systems use the 2nd power supply for "failover."

>    I see ads in Linux Journal for rack mount servers with hot-swap power
> supplies. How do these fit into your scenario above? Are they sold only to
> braindead customers?

From: plug-bounces at lists.pdxlinux.org
[mailto:plug-bounces at lists.pdxlinux.org] On Behalf Of Elliott Mitchell

You're misreading what he said. He was pointing out that most systems,
when both power supplies are operational will use *both* at somewhere
below 50% capacity; rather than one at 100% and one at 0%. The point
being that utilizing both at roughly 50% more than doubles their
lifespan. Note it is possible to load a system so heavily that you're
using more than 50% and you're no longer redundant. There is also the
situation of two smaller power supplies are cheaper than one larger power
supply.

Being over-configured can be a problem.  I use a little gizmo called
"Watts-Up" to measure the power draw of a system whenever I change its
hardware config.  It's also useful for checking the power draw through a
UPS.

Charles L. Sliger,    Information Systems Engineer,    chaz at bctonline.com
"no matter where you go, there you are..."
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