Spin Up Power Usage

[Zarathustra[H]]

Hey All,

I am trying to build a NAS FlexRAID box and trying to come up with how much of a power supply I need.

I am considering starting with 6 drives, and leaving 2 open slots for a total of 8 drives in the future. All will be WD green drives (3x3TB and 3x2TB)

I've been reading about staggered spinup lately, and I don't think the motherboard or controller I plan on using (need both to get to 8 drives) support staggered spinup, so I guess I'll need to have enough power to spin them all up at the same time.

1.) Does the label on the front of the drive stating how many amps it uses on each power line take into account spinup, or is it the steady state power usage?

2.) If it's the steady state power usage, is there a rule of thumb factor to multiply by to get the spinup power usage?

Much obliged,
Matt

 

[TheMTZ]

Hi,

1.) Does the label on the front of the drive stating how many amps it uses on each power line take into account spinup, or is it the steady state power usage?

I can't remember seeing power specs on a disk label at all. But check the data sheet of the drives you are planing to get - it will be in there. Most drives spike out at up to 30 watt's when spinning up and then idle around at 5 to 10 watts.

I currently have a 600 watt PSU in my file server with 160 watts on the 3.3 rails. No problems so far with 8 drives spinning up at once.

 

[Zarathustra[H]]

Hi,



I can't remember seeing power specs on a disk label at all. But check the data sheet of the drives you are planing to get - it will be in there. Most drives spike out at up to 30 watt's when spinning up and then idle around at 5 to 10 watts.

I currently have a 600 watt PSU in my file server with 160 watts on the 3.3 rails. No problems so far with 8 drives spinning up at once.

Like this:

0.6A at 5VDC + 0.55A@12VDC = 3+6.6 = 9.6W

Wow 30W. Really? That seems awfully high.

Thank you. I'll see if I can find spec sheets. Didn't know they published these with extra details for drives...

 

[Zarathustra[H]]

Like this:

http://images.anandtech.com/doci/4577/TCAE-3757.jpg

0.6A at 5VDC + 0.55A@12VDC = 3+6.6 = 9.6W

Wow 30W. Really? That seems awfully high.

Thank you. I'll see if I can find spec sheets. Didn't know they published these with extra details for drives...

Hmm..

For 3.0TB WD Green drives all I could see in the spec sheet was as follows:

Power Dissipation
Read/Write 6.00 Watts
Idle 5.50 Watts
Standby 0.80 Watts
Sleep 0.80 Watts

No mention of spinup.

 

[dustNbone]

I generally go by the amperage rating, assuming that the highest number indicated will occur during spin-up. Once the drive is spun up, current draw should decrease substantially.

 

[Blue Fox]

You have nothing to worry about with 8 drives. Pretty much any power supply can take that. My 400w Corsair power supply has no problem with 20 drives.

 

[Jim G]

You have nothing to worry about with 8 drives. Pretty much any power supply can take that. My 400w Corsair power supply has no problem with 20 drives.

+1 - not as many here but our Seasonic 560w has no issues powering 10 enterprise drives, two SSDs and 4 WD green drives without staggered spinup.

 

[TheMTZ]

Oh SNAP. I never noticed those voltage spec's - i must have been blind

PS - just as an example:
Deskstar 5K3000 - 3 TB, 7200 rpm version says startup 1.2 A (+5V) and 2.0 A (+12V)
http://www.hitachigst.com/tech/techlib.nsf/techdocs/02D9197756A273D0862577D50024EC1D/$file/DS5K3000_ds.pdf

 

[Red Falcon]

+1 - not as many here but our Seasonic 560w has no issues powering 10 enterprise drives, two SSDs and 4 WD green drives without staggered spinup.

Yep, my desktop has 8 older 5400RPM drives which all eat about 12watts a piece and a portable-class drive, with only a 500watt PSU, does just fine without staggered spin-up.

OP, you will be totally fine.

 

[Zarathustra[H]]

You have nothing to worry about with 8 drives. Pretty much any power supply can take that. My 400w Corsair power supply has no problem with 20 drives.

Awesome.

Just for reference, what else is in the box with the 400W supply and 20 drives?

 

[Trepidati0n]

Old school rule of thumb is 5/10/20 W (idle,operation,startup) respectively. The ratio is still fundamentally valid for platter based drives in the 7200/10k RPM class. Green drives may be a bit lower but not hugely so.

However, IIRC, the startup current will be mostly focused on the +12V (motor power) and not the +5V

 

[Zarathustra[H]]

Old school rule of thumb is 5/10/20 W (idle,operation,startup) respectively. The ratio is still fundamentally valid for platter based drives in the 7200/10k RPM class. Green drives may be a bit lower but not hugely so.

However, IIRC, the startup current will be mostly focused on the +12V (motor power) and not the +5V

Cool, thank you. What happens if the power supply is under dimensioned?

Just a slow spin up, and really long POST, or does the system fail to start at all?

 

[Zarathustra[H]]

I did some more googling and finally found my answer here.

WD Caviar Green 5th Generation Specs

2.5TB and 3TB capacities
5400 RPM
64MB cache
3Gb/s SATA
Power Consumption
Spin Up - 10.75W
Seek - 6.25W
Idle - 5.5W
Standby - 1W
Average Read Seek - 15ms
Average Latency - 5.5ms
Spindle Start Time - 17s
Error Rate - <1 in 1015

So it looks like 10.75W during spin up for the 5th gen WD green drives. Not bad.

 

[Zarathustra[H]]

So, while I was hoping to get away with a high efficiency 60W power supply, bit is evident that's not going to happen.

I'll need 8*10.75 + whatever the system uses during post. (I wish I knew what an AMD Zacate E-350 used during post). Since the TDP of the CPU and GPU are a combined 18W, I can't imagine that it's a lot, but I don't know for sure.

My Linux box won't be using the GPU, and the CPU is probably in a pretty low power state while booting, but I guess I have to err on the side of caution and assume it uses the full 18W at POST.

At this point, 8*10.75+18 = 104W is probably the smallest I should use.

 

[GeorgeHR]

So, while I was hoping to get away with a high efficiency 60W power supply, bit is evident that's not going to happen.

I'll need 8*10.75 + whatever the system uses during post.

Not really. Spin up time is so short that your power supply will not be overtaxed. (The power supply rating is most likely a rating for at least 10's of minutes before overheating and other issues arise. For the 10 seconds of spin up the power supply is not even going to notice.)

 

[brutalizer]

I am powering up 8 disks from one molex power cable. The disks stutter a lot upon boot, then it is fine and everything works well.

 

[Zarathustra[H]]

Well, I did some more reading.

I was originally intending to use a PicoPSU from mini-box.com, as it had been suggested to me that these units are much more power efficient at low watt usage than anything else.

Then I read this article showing test results that there is - at least - one traditional ATX PSU out there that achieves almost as good efficiencies at low wattages. The Seasonic SS-300SFD

According to my calculations going with the PicoPSU kit was only going to save me 3 watt over the Seasonic model above, and it would take years for this to pay off in electricity, as the Seasonic was cheaper, and didn't need as many power splitters (which are surprisingly expensive, I was expecting them to go for less than a buck) as the PicoPSU.

So I think I'm going with the 300W Seasonic now instead. I think it's a standard ATX power supply, but it does look a little strangely shaped with the fan sticking up out of the top.

 

[Trepidati0n]

Not really. Spin up time is so short that your power supply will not be overtaxed. (The power supply rating is most likely a rating for at least 10's of minutes before overheating and other issues arise. For the 10 seconds of spin up the power supply is not even going to notice.)

No. The supply will be taxed. PSU's do not have sufficient energy storage to handle several seconds (which is the spin up time of drives). Secondarily modern PSU can only go a little beyond their rated performance before they start to collapse (current limit) to protect the HW. It might work on a shit brand supply, but a good supply like a corsair, etc will have current mode regulators which are pretty eff'ing accurate.

 

[Dalfo002]

EDIT: DERP, sorry, necro'd the thread accidentally, please delete if you can