Rosewill RV350 350W Power Supply and my Backup Server

November 12, 2010

The external drive
I have had an external harddrive on my desk for a number of years. It is a 320GB Western Digital drive in a Rosewill case. It used to store data backups but as my storage needs grew, and I consolidated my various externals into a single backup machine, there is rarely a need to turn it on these days.

Looking at the poor, unused drive a few weeks back made me wonder if I had room to put it into my Windows backup machine. That headless PC currently has a CD drive, three IDE and one SATA drive. There was room, but I would have to shift things around. The CD got lowered to the bottom slot, and the new addition was placed next to the 1TB Samsung green drive in the external 3.5″ bay. Everything was hooked up, and then it was time to boot it up. I pressed the power button, got an initial hum, then nothing more, save for the power light flashing at me. I flipped the back power switch off, checked all the connections, and then tried again. Still nothing. I reasoned I had a 350 watt power supply in there so that should be plenty. I tried again, and it did boot. Success! I let it finish booting, then VNCed in and restarted the machine. Wouldn’t boot.

I dug out my handy Kill a Watt load meter and connected the machine’s plug to it. The machine idled at 110 watts, significantly less than 350. At initial power up, the machine did spike at 194 watts. I powered it back down, reconnected the fifth drive, and restarted. The machine spiked at 209 watts, an increase of 15 watts for that fifth drive. Once it fully booted, the idle load was 8W higher. Out of curiosity, I hit Newegg for the Rosewill’s specs. It appears that the power supply is rated at a “minimum of 60% efficiency at peak load”. Some quick math (350W * .6 = 210W) showed that I was requesting right at what the supply was rated for.

My thought was that this machine had been rock-solid with the existing configuration for the past four years, and now was hit and miss on boot with a fifth drive. Long-term stability seemed to be uncertain, so I powered it all down, and pulled out the drive.

I briefly considered ordering a new power supply, either a standard one with higher capacity or another 80+% efficiency model my last two machines have used. The frugal side of my personality won out; I could darn near buy another 1TB drive for the ESXi box for the price in would take to replace a perfectly functioning power supply, just to have the 320GB drive off my desk.

Further research showed that power supplies do ‘age’ over time and lose some of their efficiency. Another tidbit I found out there was is a strong correlation between weight of the PSU and the quality of it. The reasoning is that quality components just weight more. I saw that the Rosewill weighed 1.8 lbs, and the Antec used in my quads weighed 3.6 lbs.

I am posting this for the dual-purpose of showing that a entry-level 350W power supply can successfully run an XP1900+ build with four hard drives, but also that that is about its capacity. I fear a fifth drive would induce some eventual failure in another component, and that would not be good. Despite ending back where I started in the process, this was a good exercise to go through.

I’d had need to reboot this machine several times in the last week, and the PC would not start consistently. Just a hum, and then the flashing power light. Apparently the power supply was on its last legs. The Antec Earthwatts 380W Green power supply was ordered and replaced it. I was able to install the old external drive into the case, and the PC now idles at 102 watts. The initial spike of 172 watts is also much lower than the 209 of the Rosewill. This new supply is also quite a bit quieter than the old.

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