Power Adapter Barrel Size for PoE

I would be very leery of trying to use that on a two bay ReadyNAS. I don't think it would be able to push enough power over the ethernet cable. Keep in mind that you are trying to power not only two 3 1/2" hard drives but a cooling fan as well. None of these items are present in a router. My Netgear router's power block has an output of 12v @ 1 amp. The problem is similar to that seen in the difference between 2 1/2" hard drives most of which when used in an enclosure can be powered only from the USB cable and a 3 1/2" hard drive, none of which can (they all require dedicated power supplies).

I agree - PoE is not meant to run servers, it is designed for low power appliances (routers, switches, VOIP phones). I'd be worried about corrupting my data/damaging the NAS.

Got it -- I'll find a better place for my ReadyNAS. Thanks so much for your advice.

If you have an outlet close to the closet, you might run an extension cord under the door at the edge. I have an item powered that way in a closet.

I would note I have had great success powering many different devices from POE / High POE using an appropriate injector at the head end and splitter at the device end. In the case of the ReadyNAS Ultra/2 the power requirements as listed here -> http://www.readynas.com/?page_id=3962#TechnicalSpecifications note 35W typical with two 2TB drives. If you use a 4 pair high POE injector -> http://www2.microsemi.com/PowerDsine/Documentation/DataSheets/PD-9501G.pdf and a high power 4 pair splitter providing 12V -> http://www2.microsemi.com/PowerDsine/Documentation/Datasheets/PoE_951_Splitters.pdf you still have 19W (allowing for heat dissipation in the cable) of headroom (in case drive and fan spinup or boot draw more). By the numbers that setup should work- the supplied PS is rated at 2.5A@12V and the 4 pair splitter is rated at 2.5A@12V. The eBay item listed is a passive device that I could not recommend as low DC voltages do not survive long cable runs as well as higher voltages, hence the active splitter taking 50V-57V down to 12V.

Of course from a cost perspective the active POE devices I've linked are much higher and probably not worth the expense - unless you already had a multiport injector and really needed the closet to be POE powered only.

I saw some of those high voltage injectors but, as you mentioned, the cost is too high for my home setup. I'm going to end up running 30 foot ethernet and power cords. The NAS will be tucked away in a corner of the house where aesthetics are not a concern.

ahpsi wrote:

I would note I have had great success powering many different devices from POE / High POE using an appropriate injector at the head end and splitter at the device end. In the case of the ReadyNAS Ultra/2 the power requirements as listed here -> http://www.readynas.com/?page_id=3962#TechnicalSpecifications note 35W typical with two 2TB drives. If you use a 4 pair high POE injector -> http://www2.microsemi.com/PowerDsine/Documentation/DataSheets/PD-9501G.pdf and a high power 4 pair splitter providing 12V -> http://www2.microsemi.com/PowerDsine/Documentation/Datasheets/PoE_951_Splitters.pdf you still have 19W (allowing for heat dissipation in the cable) of headroom (in case drive and fan spinup or boot draw more). By the numbers that setup should work- the supplied PS is rated at 2.5A@12V and the 4 pair splitter is rated at 2.5A@12V. The eBay item listed is a passive device that I could not recommend as low DC voltages do not survive long cable runs as well as higher voltages, hence the active splitter taking 50V-57V down to 12V. Of course from a cost perspective the active POE devices I've linked are much higher and probably not worth the expense - unless you already had a multiport injector and really needed the closet to be POE powered only.

My concern here is that the 35W is typical, not worst-case - and as you indicate you need to account for cable losses. I think there is some risk that there might not be enough available power at times, and I am not sure how the NAS would deal with that. So I wouldn't personally use it for the NAS, particularly since without more people else saying that they have successfully the power system with their ReadyNAS.