Need suggestion for timer...

I'm setting up my own PC, with Port Multipliers, to run 20 Hard Drives. There will be two seperate power supplies, 1 for the machine components, another for the hard drives themselves. Now the issue is that the most power draw for a hard drive is when it starts up. And having 20 drives starting up creates a lot of power draw. So my hope is to stagger the startup of the drives. I have a switch to turn the Power Supply on without a motherboard. I need a 4-way timer, where each part will allow power through 5 seconds after the previous one. So PSU powers up, channel 1 powers up, wait 5 seconds, channel 2, wait 5 seconds, channel 3, wait 5 seconds, channel 4.

Im hoping that there is a solution that I can buy rather than build, as I have never done anything like that before. However, if theres a guide, Im willing to give it a shot. All help is much appreciated.

Darkwhisperer said:

I'm setting up my own PC, with Port Multipliers, to run 20 Hard Drives. There will be two seperate power supplies, 1 for the machine components, another for the hard drives themselves. Now the issue is that the most power draw for a hard drive is when it starts up. And having 20 drives starting up creates a lot of power draw. So my hope is to stagger the startup of the drives. I have a switch to turn the Power Supply on without a motherboard. I need a 4-way timer, where each part will allow power through 5 seconds after the previous one. So PSU powers up, channel 1 powers up, wait 5 seconds, channel 2, wait 5 seconds, channel 3, wait 5 seconds, channel 4.

Im hoping that there is a solution that I can buy rather than build, as I have never done anything like that before. However, if theres a guide, Im willing to give it a shot. All help is much appreciated.

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A typical HDD on spin-up has a combined inrush surge current of about 1 amp using 12 volt and 5 volt power. Any decent supplemental PSU should handle that without a problem. Just invest in a good single 12 volt rail PSU for your auxillary PSU.

Port multipliers are an economical solution but if I were building a system with 20 HDDs I would be thinking a few good SATA controllers with onboard processing. Much more expensive but at 20 HDDs assuming good quality HDDs you are looking at about $100 per drive for a 2K total. Why skimp on controllers?

If you really want to do this I would likely look to using a 555 timer chip in a free running 1 Hz (1 second) mode driving a decade counter like a 4017 and have those outputs toggle a 7474. There is more but that would be a start. You want to sequentially turn on HDDs so you want a sequential setup that will do that. Not real difficult but a waste of time.

My workststion PC which is pretty loaded has 10 HDDs and the entire mess, including the dual Xeon processors boots fine and runs off a single dedicated workstation PSU rated for 750 Watts. A few years old now it has 500 GB drives and never a problem. Also, my mass storage is configured in RAID 5 arrays using an Intell controller card for 6 drives and 4 driven off the motherboard. Never a problem on spin-up.

Ron

I'm not sure that a PC would like having a hard drive turn on when it isn't expecting the hard drive to turn on. Have you tried seeing how RAIDs are handled? That being said, I would expect your average power supply to be able to handle 20 hard drives if it isn't running a processor and video card.

Its good to see what the actual numbers are behind HDD power-ups. People say its of concern to have that many HDD's spinup at once, but from what you say, I think the PSU manage. The idea of using a single rail PSU didnt occur to me, thanks for that

My main aim is to have a large amount of consolidated storage with redundancy. Access speed is not a factor, and PM's are much cheaper than SATA Controllers. Initially I will start with 5 drives, and scale up as I can afford it, so its not a huge investment upfront. Indeed, the 20 drives are the largest cost of the system.

Thanks for the response

Darkwhisperer said:

Its good to see what the actual numbers are behind HDD power-ups. People say its of concern to have that many HDD's spinup at once, but from what you say, I think the PSU manage. The idea of using a single rail PSU didnt occur to me, thanks for that

My main aim is to have a large amount of consolidated storage with redundancy. Access speed is not a factor, and PM's are much cheaper than SATA Controllers. Initially I will start with 5 drives, and scale up as I can afford it, so its not a huge investment upfront. Indeed, the 20 drives are the largest cost of the system.

Thanks for the response

Click to expand...

Yeah, I have done my share of current at spinup testing and rest assured I never saw a drive peak at over an amp of combined 5 & 12 volt power. Also, for only mass stroage I see the benifit of the lower cost route. Personally I would run a pair of HDDs in RAID 1 off the motherboard controller directly then add your mountain.

Ron

You're spot on the money, that is indeed the plan