Trailing USB cable

[justin.forde_at_bankers.ie_apc]

This was originally posted on APC forums on 11/10/2010

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Hi,
I think that this is probably a really silly question but since I'm here, why not :).
We have several rack mounted servers and a SAN in the same space. We have two APC units underneath all of these. All of the power plugs for our servers and the SAN, ESX boxes etc are going into one or other UPS. So far so good. We have the Management Agent, Powerchute installed on two of the servers here so that we can manage the app through one server or the other. However, we also have a loose usb -> network connection cable coming from the SAN/ESX and I'm wondering if, in order to be supplied power in the event of power loss and/or to send the signal to the UPS which would say 'Help, I'm in trouble, you're going to have to provide me with power until AC power comes back up!', does this cable from the SAN/ESX need to be connected to one of the APCs or is this connection purely for viewing and managing the objects in Powerchute? In other words, is my SAN/ESX box protected even if I don't plug this cable into one of the APCs as I think I've run out of connections? The reason, I ask is because i'm doing the maths on whether or not our APCs are up to the task and our Load Current is apparently only 3 amps (whereas in the examples I've seen, each server is taking 4 amps) so I'm wondering are we actually protecting alot less machines than we had previously thought? As I've said the actual power connections are going from the servers, SAN/ESX etc into the power sections of the APCs. In Powerchute, I only see each server which Powerchute is installed on (one at a time, it doesn't seem to list both servers at once).
Can you advise? Many thanks in advance and apologies if I've made this query convoluted.
Justin.

Message was edited by: justin.forde@bankers.ie

[BillP]

This reply was originally posted by Angela on APC forums on 11/10/2010

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hi justin,

to begin, can you give me a little more info on the model of UPS you have? It'd be on the back of the unit most likely on a little white sticker.

also, please let me know what version of powerchute you are using - is it network shutdown or business edition?

lastly, what type of SAN do you have?

generally, a lot of SANs do support USB connectivity to the UPS to do what you described, monitor incoming power and tell the SAN to shutdown gracefully before the UPS turns off. we also support powerchute network shutdown with ESX if your UPS has a network management card so that the UPS can tell the barebones ESX box to shutdown over the network when there is an issue too. unfortunately though, we usually suggest either USB OR network connectivity for this but i dont want to say anything else before i find out what model UPS this is. also, anymore details on that USB cable? where is it plugged in now? to the UPS?

[justin.forde_at_bankers.ie_apc]

This was originally posted on APC forums on 11/12/2010

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Hi,
Actually, I spoke too soon. The cable (which seems to be a standard blue analog monitor cable on one end and a network connection on the other) is coming from one of our ESX boxes (there are don't seem to be any data connections going from our SAN into the UPS). I don't know if this cable has anything to do with the UPS or if the network connection should be talking to the UPS.
To answer your other questions, the UPS is a Smart-UPS 3000, we have Powerchute Business Edition Console V7.0.5 build 108 so it's not the Deluxe version and it doesn't seem to be set up for a graceful shutdown of the apps in the event of a power loss. Our SAN is a mirrored PowerVault MD3000.
Would you think that this analog --> network connection is to do with the UPS?
I should probably mention that having checked the 2 UPS units (one on each server), the load currents are 5.1A and 2.8A so I'm not sure if everything is being protected.
Many thanks,
Justin.

Message was edited by: justin.forde@bankers.ie

[justin.forde_at_bankers.ie_apc · Accepted solution]

This was originally posted on APC forums on 2/8/2011

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Hi,
Back to you again. Could you tell me if i'm correct in my thinking with the following calculations?
We have 2 Smart-APC 3000s each managed by a different server and each guarding the power supplies of different servers.

Unit 1 has the following figures
Load current = 2.8 A
Input/Output Voltage = 234.7 VAC

so VA Capacity is 234.7 VAC X 2.8 A = 657.16 VA

Unit 2 has the following figures

Load current = 5 A
Input/Output Voltage = 234.7 VAC

so VA Capacity is 234.7 VAC X 5 A = 1173.5 VA

Since neither exceeds our rating of 3000 VA so we’re okay with these figures. I have seen some examples in which these figures are added together and it's this figure (ie. 1830.66 VA which shouldn't exceed 3000 VA). Could you tell me if it's the two individual figures or 1830.66 VA which should be compared against 3000?). We're looking to replace at least one of these units and we'd like to know what type of calculations we need to perform. Also, would it affect the calculations if these were 2 seperate units or just 2 seperate batteries?

Watt capacity just involves multiplying these numbers by the Power Factor which for this unit is 0.9

so unit 1: 657.16 VA X 0.9 = 591.444

unit 2 = 1173.5 VA X 0.9 = 1056.15

Neither of these exceeds our rating of 2700 W so we’re okay with these figures and nor does 1647.594 exceed 2700 W.

So to recap, can you tell me if my formulae are correct, would I need to combine the 2 VA Capacity figures to compare against 3000 and the 2 Watt Capacity figures against 1647.594 since there are 2 loads or should I just compare each VA Cap figure against 3000 and each Watt Cap figure against 2700 ie. in other words, I think, is each battery rated at 3000 VA and 2700 W or is it an entire system rated at 3000 VA and 2700 W as a whole?
Apologies if I've overcomplicated this question.
Many Thanks,
Justin.