HDD power consuimption

tyeh26 · Post by **tyeh26** » Sun Mar 08, 2009 1:00 am

If SPCR tested HDDs to consume somewhere around 10W or less why do PSU calculators add somewhere around 25W per drive?

I _can_ run 3 HDDS with a E6500 and a DG45FC off a PicoPSU right?

Post by **MikeC** » Sun Mar 08, 2009 1:34 am

The only potential issue is startup current for the HDDs. Bring the platters up to speed from 0rpm takes substantially more power than any other operation of the HDD. It could be as much as double the seek/write -- but for a very brief time, I don't know the exact duration, could be well under a second.

Hitachi, which often has the most complete HDD spec sheets, cites for the 1TB 7k1000, a max start power rating of 2.0A (+12V), 1.2A (+5V) -- or around 31W total. But this is a 5-platter drive -- lots of mass for the motor to move. Most HDDs that do specify start current cite 2A max for the +12V line -- 24W.

The PicoPSU itself is rated for a total of 120W, but your 12VDC power box must be able to deliver 12V/10A to get this. To be perfectly safe (mostly during startup), you could go for the 150W version of the picopsu and a suitable hefty AC/DC 12VDC adapter -- 150W being the obvious choice. Delta makes some that rating -- not cheap, iirc.

btw-- what's an e6500? is there an Intel processor w/that model #?

blackworx · Post by **blackworx** » Sun Mar 08, 2009 2:01 am

Never done it myself, but if starting current does become an issue you might want to investigate staggered spin-up or I believe some drives now offer a feature whereby they won't spin up until needed.

tyeh26 · Post by **tyeh26** » Mon Mar 09, 2009 9:02 pm

Sorry, I meant a Pentium E5200.

This staggered spin-up looks promising, but I don't think the DG45FC has the best bios.

But If all else fails I can just do some voodoo hacks multi PSU setup that uses a more powerful PSU for the first 10 seconds right? Might take some trickery and lots of wiring though.

FaaR · Post by **FaaR** » Mon Mar 09, 2009 11:23 pm

MikeC wrote:Hitachi, which often has the most complete HDD spec sheets, cites for the 1TB 7k1000, a max start power rating of 2.0A (+12V), 1.2A (+5V) -- or around 31W total. But this is a 5-platter drive -- lots of mass for the motor to move. Most HDDs that do specify start current cite 2A max for the +12V line -- 24W.

Paradoxally, Hitachi drives actually sport the lowest real-life spin-up power draw of any 3.5" units, pretty much regardless of platter count. This has been verified in many Storagereview tests.

Most likely this is because Hitachi 3.5" units are the only HDDs that use ramps that lift the read/write head sliders off the disk surfaces when the unit is powered off. When a regular HDD spins up it has to contend with not just fighting the inertia of the platter(s), but also friction of up to eight sliders for a four-disk drive. The power difference is quite staggering, many non-Hitachi drives range between 30-40, sometimes well over 40W during spinup. Hitachi drives are typically below 20, say 15-ish or so.

Spinup is more than just a second, but less than ten. Unless you're talking about really OLD stuff. 5.25" drives stacked with as many as 10-12 disks took quite a while to spin up, and pulled some 60+ watts in the process. Heh, those were the days...

Anyway, why 3 drives? Lots of drives create terrible resonance, unless the OP has the mother of all ripped DVD libraries, why not get one 1.5TB (or even 2TB) drive to replace the other 2 units?

EsaT · Post by **EsaT** » Tue Mar 10, 2009 1:02 am

tyeh26 wrote:why do PSU calculators add somewhere around 25W per drive?

Because it's Extreme BS calculator for selling overshooting PSUs.

Use this instead:
http://web.aanet.com.au/SnooP/psucalc.php

HDD power consuimption

HDD power consuimption

Re: HDD power consuimption