Mailinglist Archive: opensuse (2496 mails)

["Brian K. White" <brian@xxxxxxxxx>]

----- Original Message ----- 
From: "Per Jessen" <per@xxxxxxxxxxxx>
To: <opensuse@xxxxxxxxxxxx>
Sent: Monday, December 01, 2008 3:38 PM
Subject: Re: [opensuse] UPS And Multiple Computers


Erland Moller wrote:

> >  Don't forget that with a bigger/more expensive UPS, most of the time
> >  you have the advantage of hot-swappable battery's and/or a bypass
> >  function plus the ability to shut down more than one server if things
> >  go wrong. Most of the small UPS's have to be shut-down to swap the
> >  battery's. Furthermore with the big UPS's the battery voltage is
> >  higher resulting in low amp's on the battery's resulting in longer
> >  lifetime.

> Erland, I think you're talking very large UPS'es here - I haven't seen
> anything less than 25kVA with hot-swappable batteries.  Bypass mode
> yes, but hot-swappable batteries is another level. 

----

I hot-swap batteries in 1 to 3 kva apc's all the time.
It's not always a one-step tray-in-socket like a hot-swap harddrive tray, but, 
a common 2200kva 2u or 3u rackmount apc has a door that opens on the front and 
you can disconnect the plug inside, pull the batts out and put new ones in and 
reconnect the plug, all while on-line.
If your unit has the connector on the back for extra external batts for more 
run-time, then you don't even ever lose protection. The power could go out 
while you are changing the internal batts and it would run on the externals. 
And of course the externals can be changed any time since they are just 
connected by a cable & a special plug anyways.

Really any ups batts can be changed while on-line, as long as you can 
physically get to the battery. The small ones make this a little dicey just 
because you don't want to be having to move the ups around to tip it on it's 
side or turn it upside down whil all the cords to the production servers are 
plugged i the back because of the risk of pulling a plug out. It would be 
better, but not strictly necessary, to schedule a graceful shutdown than to 
risk losing power during the 20 seconds while you have the battery unplugged or 
risk pulling a server power plug while moving a cheap small ups upside down.

To me hot-swap means "swap while hot", not "is convenient to swap".

The more important factor is that better ups's constantly condition the power 
and are always on-line, where the cheap ones directly connect you to the dirty 
wall power as long as there is wall power.

-- 
Brian K. White    brian@xxxxxxxxx    http://www.myspace.com/KEYofR
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