The maximum power draw a PC with many hard drives happens at boot time, in my case, the PC is a n intel atom D525MW, which hardly draws any power
What this means is that I need an oversized power supply that only does its thing at startup, then becomes an inefficient power supply right after, why this is particularly important is because this computer runs on a UPS, and the number of minutes it can stay up is a very important number.
The solution is to enable PUIS (Power up in standby), what this does is allow the disks not to spin as soon as they get power, but instead, spin up upon reception of a command from the controller. so in effect, the disks are spun up sequentially (In turn).
There are two ways to enable PUIS, the first is the Jumper method when there is a PUIS jumper on the back of the drive, which is very relevant to me as I am using western digital drives with this jumper, on the western digital website, they make no mentioning of PUIS on the jumpers page, but they tmake no mentioning of pins 3 and 4 ! turns out, Pins 3 and 4, when connected together with a jumper enable PUIS on the drive.
Te other way to enable PUIS is through hdparm, to check if it is already set, use the command
hdparm -I /dev/sdb | grep "Power-Up In Standby"
If your hard drive has it as a jumper option, the command above helps you explore if the jumper trick is working, otherwise, you need to enable PUIS using hdparm
Mind you, before i explain how to set this up in drives with no jumpers, some controllers are incompatible with this feature, so you will need to at least have a machine that is compatible to set them back if they don’t work
So, to enable PUIS, use the following command
sudo hdparm --yes-i-know-what-i-am-doing -s 1 /dev/sdb
And to set it back (Disable PUIS)
hdparm -s 0 /dev/sdb
For your reference, the following is what is mentioned on the wetern digital website about Jumpers, notice that they do not provide an explination of the relevant jumpers
