Power supply

Having all these hard drives really adds up in terms of power consumption. With 8 storage drives and a system drive, the hard drives alone will draw about 135 watts, assuming a conservative 15 watts per drive. This is a sustained current draw, during startup these values may increase by 50%. If you actually had 8 SCSI drives and ran them at peak ~2A/each, you’d need 16A on the 12V rail – even a 400W SilenX.com power supply only supplies 18A on the 12V rail. This is why many SCSI storage systems have dedicated power supplies for an external array of disk drives. Something else to consider is that a RAID array would use more power than our current setup because the drives are run simultaneously. With our design, the drive usage should be staggered. This keeps our power well under budget. Quick rule: Before you go to RAID, make sure your PSU can handle the power.

A Pentium 4 will draw about 100 watts, the video card another 70 watts, 40 watts for the motherboard, 64 watts for 1GB of DIMMS, 20 watts for a DVD-R, and another 15-25 watts or so for fans and accessories. This adds up to more than 450 watts. As you know from reading our power supply article, an advertised watt is not always a watt that gets to your components. Modern computers are increasingly relying upon the +12V voltage rail, some cheaper power supplies advertised inflated total power, when in fact the power is not where you need it. In addition, the advertised power is sometimes a peak power rating, but the calculations above imply a continuous power requirement.

Looking for the best power supply was easy. We went with the PC Power and Cooling Turbo Cool 510 ATX power supply. PC power and cooling rates their wattages as a continuous draw and also provide that rating at 40C, which is the operational temperature inside a power supply. In contrast, some power supplies are rated under ideal conditions that may not represent what is inside your server such as 25C. There is an interesting brochure about this on the PC Power and Cooling website. We all know the value of clean power; the PC Power and Cooling Turbo Cool 510 has an integrated line conditioner. This power supply provides 34A on the +12v with a peak of 38A.

The PC Power and Cooling PSU

It doesn’t look as fancy as some of the other supplies on the market, but they do offer an all black model with techflex sleeving on the wire bundles. This power supply is also one of the few that offer a Serial ATA connection with a +3.3V line. The cables are very generous in length and will easily reach your drives, even in the biggest of cases. It includes a power cable, but one that is only 18 gauge. Server power cables usually are 16 gauge. Supermicro bundles a 16 gauge power cable with its 450 watt power supply.

PC Power and Cooling also warranties their power supplies for 5 years, which is 4 more than the industry standard. Remember, we are looking to build the most reliable system for the money. This power supply does cost more, but compared to the competition, there really isn’t any competition until you get to the multiply redundant server power supplies that cost much more.

Cost: $190 at www.pcpowerandcooling.com