• Redundant power supplies

    From Don Y@21:1/5 to All on Sat Oct 26 23:54:01 2024
    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?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to blockedofcourse@foo.invalid on Sun Oct 27 12:28:27 2024
    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.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to blockedofcourse@foo.invalid on Sun Oct 27 10:59:41 2024
    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.

    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?

    Using two diodes is sure easy.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to legg on Sun Oct 27 14:12:44 2024
    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? :>

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to blockedofcourse@foo.invalid on Sun Oct 27 18:17:37 2024
    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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to legg on Sun Oct 27 17:03:23 2024
    On 10/27/2024 3:17 PM, legg wrote:
    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.

    So, the server manufacturer (Dell in this case, HP in others)
    are just engaging in marketeering. And, their customers haven't
    yet caught on? Having the ability to specify *a* primary power
    supply will be regarded as a *feature*??

    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.

    Everything is a study in probabilities. The chances of TWO units failing
    is less likely than *one* failing. You weight the value of the system (resource) being accessible with the probability of some number of
    failures taking it down.

    - 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.

    So, you don't *know* why the setting is there and why altering it
    affects which of the redundant power supplies carries the load
    when the machine is first powered on...

    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.

    Verified to be the case -- unlike the other servers.

    Hot-swap hardware is easily identifiable, as they physically
    pull-out / push-in. No disassembly required.

    Exactly. My fans, power supplies, disk drives are all hot-swappable
    or hot-spare (including DRAM).

    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.

    The "BIOS"/Setup is a common interface for the administrator to specify parameters governing the operation of the hardware. Just like setting
    the real-time clock, determining boot order, configuring RAID
    controllers and volumes, update firmware, etc. It's just a
    convenient place for "settings" that affect the operation of the
    device to be accessed by the user (or, through ILOM/iDRAC/etc.).

    Or, we could go back to *hardwiring* options...

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to Don Y on Sun Oct 27 20:00:31 2024
    On 10/26/2024 11:54 PM, 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?

    And, why would I ever want to *disable* PFC?

    I heard from a friend who manages a server farm.

    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%!]

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Lasse Langwadt@21:1/5 to Don Y on Mon Oct 28 23:22:06 2024
    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

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Lasse Langwadt on Mon Oct 28 22:42:34 2024
    Lasse Langwadt <llc@fonz.dk> wrote:
    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


    The two best things about equal sharing are that the supplies run cooler
    and that you always know that the backup supply is working.

    Otherwise you risk cascading failures a la Three Mile Island.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to Lasse Langwadt on Mon Oct 28 16:11:40 2024
    On 10/28/2024 3:22 PM, Lasse Langwadt wrote:
    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

    Then why not say "Connect PS#1 to your preferred source of power,
    if you have one"? I.e., why add a setting AND hardware that
    allows the system to "pick" one over the other?

    The downside would be that access to the PDU might not be convenient, especially for the guy running the farm (its no fun walking down the
    hot aisle!)

    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

    Possibly. The reason I have been given has to do with energy efficiency
    (even at low loads -- like "sleep" power).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to Don Y on Tue Oct 29 23:33:49 2024
    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!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to blockedofcourse@foo.invalid on Wed Oct 30 08:54:28 2024
    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.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to legg on Wed Oct 30 13:22:12 2024
    On 10/30/2024 5:54 AM, legg wrote:
    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.

    That depends on how much is handled "inboard" of the power supplies.
    Obviously, the power system has been designed to support the rated
    load of the individual power supplies *during* such a hand-over.
    And, regardless of mains voltage (autoranging) or power line
    frequency.

    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.

    Not the case, here. These are marketed as hot-swappable.

    It's a connector pin sequencing and dynamic start-up/shutdown/
    engagement performance issue.

    GND pins make first and break last.

    Additionally, the system involved (memory, power, storage)
    has protocols to make this a graceful transition and indicators
    to convey the state of that protocol. I have laminated
    cheat-sheets (business card sized) for each host to know
    how to affect those changes on that particular host as
    there is no "standard".

    E.g., the power supplies indicate when they can be swapped
    out via an indicator on the supply. They indicate when
    they *should* be swapped out (mismatched, etc.) using the
    same indicator. The log and front panel provide more
    human readable indications.

    Storage devices that are part of a managed array will
    typically idle themselves when failed. Or, indicate
    when they are being rebuilt. SATA/SAS devices can be
    treated as hot-swappable if you umount() them to ensure they
    are quiescent.

    [I suspect MS "server" OS's have this covered in the
    Management Console. In the *BSDs, I've found you
    have to go through several explicit steps to unmount,
    remove, reattach, reprobe, remount replacement volumes)]

    But, even subsystems that don't explicitly support hot-swap
    can be coerced to do so. You just can't do so "willy-nilly"
    and expect the device not to incur a loss.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jasen Betts@21:1/5 to Don Y on Sat Nov 2 09:08:58 2024
    On 2024-10-27, 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.

    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?

    Perhaps if your power source is an inverter, or even DC


    --
    Jasen.
    🇺🇦 Слава Україні

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)