Powering a ton of drives...

[middle_pickup]

I'm looking at building a new Plex server with a ton of hard drives, and I am trying to decide on a PSU. How do you determine how many sata devices a power supply can safely power? I've seen sata power splitter cables with one female and 4 male connectors. Are these kinds of cables safe for all power supplies? I would like to be able to power up to 18 drives safely. I'm just kind of confused because I see only two or three sata power outputs on most modular power supplies.

[BondiBlue]

It depends on the PSU as well as the drives. A few years ago I needed to run many drives in an old Dell OptiPlex 755. That particular PSU had no issue spinning up 10 old mechanical hard drives all at once. It only has four native SATA connectors too, so I was far exceeding the expected output of it. 

 

11 minutes ago, zjdrummond said:

I'm just kind of confused because I see only two or three sata power outputs on most modular power supplies.

Are you looking at the PSU itself to determine that number? If so, each one of those connectors will typically be used with a cable that has multiple SATA connectors on it. The number of connectors depends on the model of the PSU though. 

[middle_pickup]

22 hours ago, BondiBlue said:

Are you looking at the PSU itself to determine that number? If so, each one of those connectors will typically be used with a cable that has multiple SATA connectors on it. The number of connectors depends on the model of the PSU though. 

I'm still new to building computers. I have an EVGA G2 with two SATA power ports in my current PC. There's also a peripheral power port. Can you use these kinds of outputs for SATA too? I just want to make sure that I know how to pick a PSU with enough ports safe to use with SATA connectors, and that I will have enough power to safely power the maximum number of drives I want to build out to eventually-18 drives.

[Guest]

Are these SSDs or are you spinning rust? 

[middle_pickup]

17 minutes ago, jonnyGURU said:

Are these SSDs or are you spinning rust? 

Going for max storage so I'll use mostly hard drives, but I will want a couple of SSD's for plex cache and maybe an extra boot drive.

[Guest]

Hmm.. So the hardest part about firing up a lot of drive is not that there isn't enough power to keep them spinning, but getting them all to spin up and detected.  The power required to pin up multiple drives at the same time is relatively huge.  That's why file servers tend to use "staggered start up" when using old platter drives.

 

[IntelJoe]

Not sure how helpful this information is. But I run a C2100 with 12x 2TB spinning drives. It has dual 750w PSU's and will spin up/operate on one PSU.

[middle_pickup]

 

Linus did a 20 drive server much like I intend to build, but didn't at all mention the PSU. It doesn't seem like power was at all a hard thing to do for him. Wish I could get a straight answer here.

[SavageNeo]

6 hours ago, zjdrummond said:

 

Linus did a 20 drive server much like I intend to build, but didn't at all mention the PSU. It doesn't seem like power was at all a hard thing to do for him. Wish I could get a straight answer here.

well you have to look how much power you psu delivers at 5V, or at 12V, depends on the drive. for 18 drives ypu want around 200w on the 5v rail which is a lot. so ou need atleast 40A on the 5V assuming all your HDDs use 5V and not 12V and counting all the other things that use 5V rail

[mariushm]

A hard drive consumes some amount of power on 5v for the chips on the circuit board, and some power on 12v for the motor.

The motor will consume 2-3 times more power than the normal power consumption for a few seconds as it starts up.

SOME hard drives use 5v motors, so they'll only draw power from 5v, but such drives are not common. 

 

For most hard drives, the power consumption is around 3-5 watts on 5v and around 4-6 watts on 12v

 

For example, see the datasheet of WD Black which is a bit more power hungry than average drives: data-sheet-wd-black-pc-hard-drives-2879-771434.pdf

 

You can see it says 9.1w active, 7.1w idle,  1.0w sleep  so you can kind of extrapolate from it the motor consumes around 6w and the electronics 3w

 

Here's the WD Red Plus (NAS using CMR) : FC41D42F91D9521789B0A1CBBBB0A486977F1BC5_PRODUCTBRIEFWESTERNDIGITALWDREDPLUSHDD_source.PDF

 

Note that it says on the 14 TB model  PEAK at 12v  1.85A ,  read/write or active 6.5w , idle 3.0w and sleep 0.8w so because these run at around 5400-5900 rpm

The 10 and 8 TB models are more power hungry, at around 8.4w/8.8w active and 4.6w/5.3w idle  but still below the wd black - my guess would be either they use a 7200 rpm motor based on the higher noise levels listed, or the 8 and 10 TB models use an older generation platters with less data density and therefore there's extra platter, making the motor consume less power to spin them, and more power used because more heads to operate.

 

So anyway, I'd say reserve 0.75A on 5v for each mechanical drive.  Assume your power supply can give 15-20A on 5v, and that around 5A will be consumed by the PC components (onboard chipset, onboard audio, onboard network, if the motherboard doesn't power those directly from 3.3v or uses dc-dc converters to convert 3.3v to lower voltages, keyboard, mouse).

You're left with maybe 10A available on 5v so around 10/0.75 = 13 drives

 

Then account for the peak power consumption if all drives spin up at same time... ex if you have 12 drives all with peak power of 1.85A, there goes 12 x 1.85 = 22A of current on 12v

 

Keep in mind majority of power supplies have a total "budget" for both 3.3v and 5v, let's say 120w, and they have independent dc-dc converters that produce 3.3v and 5v from that budget of 120 watts

[middle_pickup]

15 hours ago, mariushm said:

A hard drive consumes some amount of power on 5v for the chips on the circuit board, and some power on 12v for the motor.

The motor will consume 2-3 times more power than the normal power consumption for a few seconds as it starts up.

SOME hard drives use 5v motors, so they'll only draw power from 5v, but such drives are not common. 

 

For most hard drives, the power consumption is around 3-5 watts on 5v and around 4-6 watts on 12v

 

For example, see the datasheet of WD Black which is a bit more power hungry than average drives: data-sheet-wd-black-pc-hard-drives-2879-771434.pdf

 

You can see it says 9.1w active, 7.1w idle,  1.0w sleep  so you can kind of extrapolate from it the motor consumes around 6w and the electronics 3w

 

Here's the WD Red Plus (NAS using CMR) : FC41D42F91D9521789B0A1CBBBB0A486977F1BC5_PRODUCTBRIEFWESTERNDIGITALWDREDPLUSHDD_source.PDF

 

Note that it says on the 14 TB model  PEAK at 12v  1.85A ,  read/write or active 6.5w , idle 3.0w and sleep 0.8w so because these run at around 5400-5900 rpm

The 10 and 8 TB models are more power hungry, at around 8.4w/8.8w active and 4.6w/5.3w idle  but still below the wd black - my guess would be either they use a 7200 rpm motor based on the higher noise levels listed, or the 8 and 10 TB models use an older generation platters with less data density and therefore there's extra platter, making the motor consume less power to spin them, and more power used because more heads to operate.

 

So anyway, I'd say reserve 0.75A on 5v for each mechanical drive.  Assume your power supply can give 15-20A on 5v, and that around 5A will be consumed by the PC components (onboard chipset, onboard audio, onboard network, if the motherboard doesn't power those directly from 3.3v or uses dc-dc converters to convert 3.3v to lower voltages, keyboard, mouse).

You're left with maybe 10A available on 5v so around 10/0.75 = 13 drives

 

Then account for the peak power consumption if all drives spin up at same time... ex if you have 12 drives all with peak power of 1.85A, there goes 12 x 1.85 = 22A of current on 12v

 

Keep in mind majority of power supplies have a total "budget" for both 3.3v and 5v, let's say 120w, and they have independent dc-dc converters that produce 3.3v and 5v from that budget of 120 watts

Okay cool. This is super helpful. I'm starting to get it I think. I'm probably going to be using mostly NAS drives like those from WD and the Seagate iron wolf stuff. I have a couple of those already.