On Wed, 22 Dec 2021 at 17:05, Roger Heflin <rogerheflin@xxxxxxxxx> wrote:
Usually a spinning disk need about 1amp at 12v to spin up each disk. I have had to upsize a power supply because the original ps was no longer quit big enough after the disks had aged and increased startup current closer to the max specified for the disk. Max x disks was a few amps over the ps rating, but worked when the disks were new.
I'm not surprised, but I learned to replace disks at end-of-warranty. In the early years not many lasted the warranty period with our workloads (constantly filling and emptying disks), but now manufacturers have got things dialed in so the failure rate soars after end-of-warranty. (Ferrups)
If your 3kva ups shuts off on a 1.2kva load that means it has a battery with at least one dead cell in it. If multiple new batteries are in it you need a load tester to put a load on the batteries and see which one has a low voltage. I have had to do that on a 7.5kva/4×12v system and at idle all 4 batteries voltages look about the same, but under load one battery was about 2v low. My batteries were under 12 month warranty still so i was able to get a new one sent.
For the mission-critical systems we used BEST Ferrups (retired from sea-duty) and then APC. Both had good battery tests and we ran them regularly because a UPS failure could mean losing irreplaceable satellite downlink data (corollary to Murphy's Law -- power is most likely to fail during time-critical processing stages)..
It was the 1.4 KVA UPS that rejected the startup load. The 3KVA unit actually had new batteries configured well below maximum capacity because we only needed it to hold up long enough to be sure the generator had come online before starting a shutdown.
On Wed, Dec 22, 2021, 2:46 PM George N. White III <gnwiii@xxxxxxxxx> wrote:On Wed, 22 Dec 2021 at 10:36, Tim via users <users@xxxxxxxxxxxxxxxxxxxxxxx> wrote:On Fri, 2021-12-03 at 10:45 +1030, Tim via users wrote:
[...]It's scary when you see PCs with 500 watt power supplies (or the
hardware manuals saying you need one), but they don't use 500 watts all
the time, if at all. It's just their capability. The main idea is
that a beefy power supply doesn't have any problems when everything
cold boots. Probably the only thing that's really going to cause the
average user's PC to use a lot of power is gaming with fancy on-the-fly
graphics rendering.Spinning up a bunch of rotating media disks can be a problem booting. Evenif the server has a big power supply, your UPS may not handle the load. I usedget around that by booting from a small disk and manually mounting the RAIDarray. Newer disks do use a fraction of the power of older models. butlower prices just mean people stuff boxes with as many drives as it canhold. Maybe current systems are smarter about staging drive startup.It isn't only gaming that that is power hungry -- vendors have to consider arange of use cases. My group at work once got the loan of a high-end Dellworkstation that had been used as a node in a large numerical model. Onboot the system immediately started heavy numerical processing andthe 1.4 KVA UPS cut it off. The manual said it needed 1200 VA power.Fortunately we had a 3KVA UPS originally used for deskside SGI "mini-super"system.
--
George N. White III
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