How much power will I need for this setup?

sthayashi · Post by **sthayashi** » Fri Nov 21, 2003 10:46 am

I'm putting together a file server that will also act as my router as well as my linux tinkertoy. Basically it's a computer with a NIC, a RAID controller card and a dozen drives.

The setup is/will be as follows:
-Asus P2B-D2 w/ 2 PIII/550 processors.
-cheapy video card
-3com NIC.
-8 drive SATA RAID controller (haven't figured out if I should go with 3ware, Highpoint or wait for the one reviewed by Tom's Hardware

(yeah, I know the stigma around here).
- 8-12 drives. They'll either be Samsung or Seagate (probably Samsung).
-floppy
-Toshiba DVD-Rom.

Ideally, I'd like it to be a quiet power supply, since this machine will be tucked in the corner of my apartment. I'd even be willing to get 2 Power supplies if it means it'll be quieter. I think right now I have a PC Power and Cooling P/S, and it's NOT quiet.

Any recommendations/suggestions?

Trip · Post by **Trip** » Sat Nov 22, 2003 6:41 am

BUMP

EDIT: I looked at the posting date wrong, this was only posted yesterday...

Tigr · Post by **Tigr** » Sat Nov 22, 2003 10:38 am

Hi!

So, each HDD will consume circa 10W maximum. For 12 drives, this means 120W. There is also an issue of spin-up current and I am not completely sure what the spec of Samsung is. This site specifies 820 / 2250 mA. Assuming

that they mean 820 mA on 5V and 2250 mA on 12 V (and I may be seriously wrong on this) you get the total of:
5V: 820*12=9840mA (10A)
12V: 2250*12=27000mA (27A)
The PSU must be able to sustain 10A on 5V rail and 27A on 12V rail for a short period of time at start-up(plus the consumption of the rest of the machine). The peak power would be 5*10+12*27=374Watt

So, basically, if I assume that the rest of components will consume about 150 Watts (Ihave no idea of dual PIII consumption really), you can get away with a 300W PSU during the normal run of your system. However, the large spin-up consumption of the disks will mean that a 500W PSU would be wise.

Please, calculate your board consumption, don't rely on my assumptions, ok?

HTH

EDIT: And I completely forgot the power factor. That is, no PSU is 100% efficient. So, you will have to get more powerful PSU than the figures indicate. How much more - depends on the efficiency of the PSU.

sthayashi · Post by **sthayashi** » Sat Nov 22, 2003 6:22 pm

What's the best way to calculate the power consumption of the board? Asus has been quiet about this, and I can't seem to google up a good answer.

Thanks again. I'll probably go with the Antec TruePower 550, which I have currently in my main computer, a dual athlon box, but then I have to figure out what the power consumption for THAT computer.

Inexplicable · Post by **Inexplicable** » Sun Nov 23, 2003 1:18 am

Tigr wrote:5V: 820*12=9840mA (10A)
12V: 2250*12=27000mA (27A)
The PSU must be able to sustain 10A on 5V rail and 27A on 12V rail for a short period of time at start-up(plus the consumption of the rest of the machine). The peak power would be 5*10+12*27=374Watt

When buying the PSU it's important to pay close attention to the max imum current on each rail rather than looking at the total wattage. For the 5V rail you need 10A for the 12 drives. For the 12V rail, you need 10A during normal use and 27A during spinup (worst case). The 12V rail is clearly the limiting one here.

sthayashi -- make sure your mobo can spin up the drives in a staggered fashion rather than spinning them up simultaneously. This can significantly reduce the peak current requirement and allow you to use a smaller PSU.

sthayashi · Post by **sthayashi** » Sun Nov 23, 2003 1:59 pm

Inexplicable wrote:make sure your mobo can spin up the drives in a staggered fashion rather than spinning them up simultaneously. This can significantly reduce the peak current requirement and allow you to use a smaller PSU.

Again, how would I go about insuring this? This sounds like something the raid card should be able to do (since most of these drives will be on the raid card).

Thanks for the input though. It looks like not even the Antec TruePower550 can take the load of 12 samsung drives spinning up at the same time. This is where I say F***! There has to be a way to set something like that up.

Inexplicable · Post by **Inexplicable** » Sun Nov 23, 2003 2:21 pm

sthayashi wrote:Again, how would I go about insuring this? This sounds like something the raid card should be able to do (since most of these drives will be on the raid card).

Yeah, the BIOS on the RAID card must support this. Should be a fairly standard feature but look at the data sheets or ask the vendor before you buy.

Tigr · Post by **Tigr** » Tue Nov 25, 2003 7:37 am

Inexplicable wrote:
sthayashi wrote:Again, how would I go about insuring this? This sounds like something the raid card should be able to do (since most of these drives will be on the raid card).
Yeah, the BIOS on the RAID card must support this. Should be a fairly standard feature but look at the data sheets or ask the vendor before you buy.

If I understand correctly, the SCSI cards do that normally, i.e. they spin up the drives one-by-one. I do not know if there are IDE RAID cards that can do the same but it is definitely worth looking for.