Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
I have always *assumed* they were configured to SHARE the load.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
And, why would I ever want to *disable* PFC?
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
I have always *assumed* they were configured to SHARE the load.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
And, why would I ever want to *disable* PFC?
On Sat, 26 Oct 2024 23:54:01 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
What kind of 'boxes' are you talking about?
Redundancy is seldom a feature outside the military,
telecom, life-support or un-interruptible fields.
I have always *assumed* they were configured to SHARE the load.
Sharing is not a feature required for redundancy.
Failure isolation IS.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
The former doesn't make any sense
- the latter is a simple matter
of voltage adjustment differential and degrees of slope compensation
in the sharing scheme. Some digital/software guys can get carried
away - offering features that don't make any particular sense,
just because they can . . . . . Simple is usually better when it
comes to power delivery, regulation and security.
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
Switch-over and single-fault failure characteristics can vary
between different set-ups. The aim is to provide minimal
disturbance to the system when one unit fails, or when one
unit has to be hot-swapped out.
Hot-swapping is not automatically feasible, just because there
are two power supplies in parallel. It could be that the
option to select a 'primary' unit is a crude attempt to
provide quasi hot-swap capability.
And, why would I ever want to *disable* PFC?
Non-sequitur. Power Factor Correction has nothing to do with
redundancy. See previous comments re digital/software.
On 10/27/2024 9:28 AM, legg wrote:
On Sat, 26 Oct 2024 23:54:01 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
What kind of 'boxes' are you talking about?
Redundancy is seldom a feature outside the military,
telecom, life-support or un-interruptible fields.
Servers. Most (except cheap ones) have redundant power supplies.
Even some of my "non-server" boxes are so equipped.
I have always *assumed* they were configured to SHARE the load.
Sharing is not a feature required for redundancy.
Failure isolation IS.
So far, every box that I've checked, "shares" the load (as
indicated by draw on the mains) to within about 10%. Unplugging
either supply causes the other to carry the full load (reflected
by the "doubling" of mains power consumption)
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
The former doesn't make any sense
It would "make sense" if one supply was selected to carry the
entire load while the other was on standby to cover the case when
the "primary" failed. Though it seems like it would be easier to
just say "PS #1 is primary" and let the user recable the box if
required.
OTOH, if #1 is toast (or, not present), then selecting it as the primary >would be foolhardy. (One assumes the system would immediately switch
to #2)
I just don't see why you couldn't use a simple diode switch to
pick a single supply (despite the fact that there are multiple
output voltages... you wouldn't want supply #1 to carry V3 and
supply #2 to carry V1 & V2).
- the latter is a simple matter
of voltage adjustment differential and degrees of slope compensation
in the sharing scheme. Some digital/software guys can get carried
away - offering features that don't make any particular sense,
just because they can . . . . . Simple is usually better when it
comes to power delivery, regulation and security.
The "software guy" likely was told he had to control a setting
that the *hardware* guy had created.
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
Switch-over and single-fault failure characteristics can vary
between different set-ups. The aim is to provide minimal
disturbance to the system when one unit fails, or when one
unit has to be hot-swapped out.
Hot-swapping is not automatically feasible, just because there
are two power supplies in parallel. It could be that the
option to select a 'primary' unit is a crude attempt to
provide quasi hot-swap capability.
The server in question is probably the most recently designed
(though no idea where it sits on the marketing scale of "trim level")
I will be working with it, next, so will watch to see *if* it
does, indeed, draw all of its mains power from a single supply.
And, why would I ever want to *disable* PFC?
Non-sequitur. Power Factor Correction has nothing to do with
redundancy. See previous comments re digital/software.
It wasn't expected to relate. Rather, the setting is lumped
together with other power-related settings in the "BIOS".
Should I have created another thread to ask that? :>
On Sun, 27 Oct 2024 14:12:44 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
On 10/27/2024 9:28 AM, legg wrote:
On Sat, 26 Oct 2024 23:54:01 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
What kind of 'boxes' are you talking about?
Redundancy is seldom a feature outside the military,
telecom, life-support or un-interruptible fields.
Servers. Most (except cheap ones) have redundant power supplies.
Even some of my "non-server" boxes are so equipped.
Servers are telecom, if the guy who labelled it has been
paying attention. Obviously most PC's can do the job, but
that doesn't qualify them to do it.
I have always *assumed* they were configured to SHARE the load.
Sharing is not a feature required for redundancy.
Failure isolation IS.
So far, every box that I've checked, "shares" the load (as
indicated by draw on the mains) to within about 10%. Unplugging
either supply causes the other to carry the full load (reflected
by the "doubling" of mains power consumption)
Nice to have; can make other features easier; but again, not
critical to redundancy.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
The former doesn't make any sense
It would "make sense" if one supply was selected to carry the
entire load while the other was on standby to cover the case when
the "primary" failed. Though it seems like it would be easier to
just say "PS #1 is primary" and let the user recable the box if
required.
OTOH, if #1 is toast (or, not present), then selecting it as the primary
would be foolhardy. (One assumes the system would immediately switch
to #2)
Select schmellect. You can't account for stupidity.
I just don't see why you couldn't use a simple diode switch to
pick a single supply (despite the fact that there are multiple
output voltages... you wouldn't want supply #1 to carry V3 and
supply #2 to carry V1 & V2).
It's not possible to claim redundancy without safe isolation in
the event of single-point abnormals, including direct output
short of each unit, individually. Diode or 'active' rectifier
isolation is basic.
An active rectifier may be disabled (open circuit), as a form
of intentional isolation for diagnostic testing.
Another 'simple' feature is margining or straight 'soft' disable.
You wouldn't normally use all of these features outside a
triple redundant system, or a single unit test could bring the
system down, if the 'second' unit had already failed.
- the latter is a simple matter
of voltage adjustment differential and degrees of slope compensation
in the sharing scheme. Some digital/software guys can get carried
away - offering features that don't make any particular sense,
just because they can . . . . . Simple is usually better when it
comes to power delivery, regulation and security.
The "software guy" likely was told he had to control a setting
that the *hardware* guy had created.
Power supplies are designed and tested to spec, in and out of
the end-use system. . . . . but they can just be thrown into
another syatem, after the fact, without the same scrutiny.
Just because you CAN do something, doesn't make it either
sensible, logical or worthwhile, out of context.
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
Switch-over and single-fault failure characteristics can vary
between different set-ups. The aim is to provide minimal
disturbance to the system when one unit fails, or when one
unit has to be hot-swapped out.
Hot-swapping is not automatically feasible, just because there
are two power supplies in parallel. It could be that the
option to select a 'primary' unit is a crude attempt to
provide quasi hot-swap capability.
The server in question is probably the most recently designed
(though no idea where it sits on the marketing scale of "trim level")
I will be working with it, next, so will watch to see *if* it
does, indeed, draw all of its mains power from a single supply.
Hot-swap hardware is easily identifiable, as they physically
pull-out / push-in. No disassembly required.
This is not a minor design consideration and is coordinated
in the frame, connectors and other hardware to allow
seamless power delivery throughout.
And, why would I ever want to *disable* PFC?
Non-sequitur. Power Factor Correction has nothing to do with
redundancy. See previous comments re digital/software.
It wasn't expected to relate. Rather, the setting is lumped
together with other power-related settings in the "BIOS".
Should I have created another thread to ask that? :>
Power supplies don't know bios. Perhaps it's a confused acronym for
something else.
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
I have always *assumed* they were configured to SHARE the load.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
And, why would I ever want to *disable* PFC?
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
I have always *assumed* they were configured to SHARE the load.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
And, why would I ever want to *disable* PFC?
On 10/27/24 07:54, Don Y wrote:
Most of my boxes have dual power supplies.ÿ Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
I have always *assumed* they were configured to SHARE the load.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??).ÿ And, when in the redundant configuration,
allows me to choose which is the "primary".
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
I would guess if you wanted to power one of them from a "preferred" powersource and the other from a another source that you don't want
to load unless you have to
And, why would I ever want to *disable* PFC?
when you have an UPS that doesn't have sinewave output, they don't
always play nicely with PFC
On 10/27/24 07:54, Don Y wrote:
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
I have always *assumed* they were configured to SHARE the load.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
I would guess if you wanted to power one of them from a "preferred" powersource
and the other from a another source that you don't want
to load unless you have to
And, why would I ever want to *disable* PFC?
when you have an UPS that doesn't have sinewave output, they don't always play
nicely with PFC
Apparently the settings have nothing (little?) to do
with reliability/redundancy. Rather, they are there
to improve energy efficiency (!)
From the long list of settings he sent me, these people REALLY
try to save every watt they can! I guess if you have
thousands of servers, a few watts on each has consequences
(cooling, etc.).
[As a quick test, I was able to change the power requirements
for my server addressing a fixed load by more than 10%!]
On 10/27/2024 8:00 PM, Don Y wrote:
Apparently the settings have nothing (little?) to do
with reliability/redundancy. Rather, they are there
to improve energy efficiency (!)
From the long list of settings he sent me, these people REALLY
try to save every watt they can! I guess if you have
thousands of servers, a few watts on each has consequences
(cooling, etc.).
[As a quick test, I was able to change the power requirements
for my server addressing a fixed load by more than 10%!]
After playing with assorted setting combinations, it
is obvious that they do nothing to affect the (shortterm)
availability of the server.
When configured to share the load, the load is approximately
split evenly between the two supplies -- if both are powered on.
Unplug either and the other takes the full load.
When configured as hot spare, select PS#1 as "primary", unplug
that power cord and PS#2 "spins up" to take on the load.
Unplug PS#2 and, as expected, no change (other than a
warning indicating that you are now completely reliant on
that ONE power supply).
*BUT*, the total power consumed goes UP when the load
is shared if the power supplies are "lightly" loaded.
This makes sense as efficiency tends to improve with
the magnitude of the load.
In my case, there was about a 25W "penalty" for operating
in the sharing configuration (on a ~220W load -- single CPU,
external SAS HBA, 8x1TB, 256GB DRAM).
Moral of story is to size individual power supply to handle
the entire (projected/future) load and then use the hot spare
to give you redundancy. So, this is an enhanced feature that
isn't available in my other servers...
[Amusing as I tend to oversize the power supplies to address
unknown future needs... annoying to have to upgrade a power
supply -- PAIR of power supplies -- just because you want to
embelish the hardware in a box!]
But, still no idea why I should be able to *select* the primary
supply if both are cabled!
On Tue, 29 Oct 2024 23:33:49 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
On 10/27/2024 8:00 PM, Don Y wrote:
Apparently the settings have nothing (little?) to do
with reliability/redundancy. Rather, they are there
to improve energy efficiency (!)
From the long list of settings he sent me, these people REALLY
try to save every watt they can! I guess if you have
thousands of servers, a few watts on each has consequences
(cooling, etc.).
[As a quick test, I was able to change the power requirements
for my server addressing a fixed load by more than 10%!]
After playing with assorted setting combinations, it
is obvious that they do nothing to affect the (shortterm)
availability of the server.
When configured to share the load, the load is approximately
split evenly between the two supplies -- if both are powered on.
Unplug either and the other takes the full load.
When configured as hot spare, select PS#1 as "primary", unplug
that power cord and PS#2 "spins up" to take on the load.
Unplug PS#2 and, as expected, no change (other than a
warning indicating that you are now completely reliant on
that ONE power supply).
*BUT*, the total power consumed goes UP when the load
is shared if the power supplies are "lightly" loaded.
This makes sense as efficiency tends to improve with
the magnitude of the load.
In my case, there was about a 25W "penalty" for operating
in the sharing configuration (on a ~220W load -- single CPU,
external SAS HBA, 8x1TB, 256GB DRAM).
Nothing is free, but you will have double the hold-up time.
Moral of story is to size individual power supply to handle
the entire (projected/future) load and then use the hot spare
to give you redundancy. So, this is an enhanced feature that
isn't available in my other servers...
[Amusing as I tend to oversize the power supplies to address
unknown future needs... annoying to have to upgrade a power
supply -- PAIR of power supplies -- just because you want to
embelish the hardware in a box!]
But, still no idea why I should be able to *select* the primary
supply if both are cabled!
Not all redundant supplies are hot swappable - but rely on the
supply being pulled/inserted to be in a disabled/dead or powered
down state.
It's a connector pin sequencing and dynamic start-up/shutdown/
engagement performance issue.
Most of my boxes have dual power supplies. Most
don't give me an option as to how they are used/configured;
one shits the bed, the other is there to cover the load.
I have always *assumed* they were configured to SHARE the load.
I picked up another box that gives me the option of NOT operating
them redundantly (what the hell does the "extra" one do, just
sit around??). And, when in the redundant configuration,
allows me to choose which is the "primary".
This suggests one is carrying the load and the other is switched
in (even if passively) when that one fails.
Is there any advantage to this over a "sharing" configuration?
And, why would I ever want to *disable* PFC?
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