SATA Connector Power Rating and Hard Drives

SATA power connectors, according to ATX standards, are rated for ~75 W total, but power supplies usually slightly exceed it. Nevertheless it’s easy to exceed this number if you’ve a large number of HDDs plugged into a system. In this article, I’ll take a deeper look into this issue and explore solutions to prevent power-related problems.

A SATA power connector is rated to provide up to 1.5 A per pin (source here), and since each voltage rail (5 V and 12 V) uses 3 pins in parallel, that means:

• 3 pins per rail => 3 * 1.5 A = 4.5 A total
• 5 V rail => 5 * 4.5 = 22.5 W
• 12 V rail => 12 * 4.5 = 54 W

However, your biggest problem is on drive spin-up when you turn on the system, at that point you’ve 10 drives pilling a lot of power, potentially exceeding 75 W for a few seconds.

To get around this problem you have two options: 1) enable “staggered spin-up” or “HIPM” / “DIPM” in your UEFI… or 2) use a software-based approach.

If your UEFI doesn’t support “staggered spin-up”, you can use the “power-on in standby” (PUIS) mode available on most modern hard drives. This feature prevents the drive from spinning up automatically when power is applied, allowing the system to control the spin-up. It’s a persistent setting that survives reboots and power cycles, making it a reliable workaround for systems without native staggered spin-up support.

# Check if your drive supports it with:
hdparm -I /dev/sdb | grep "Power-Up In Standby"

# Enable with:
hdparm -s 1 /dev/sdb

Note that this does tell the drive to not start spinning, but for the drives to wait until the correct command is received to do a spin-up. In short, this means that instead of auto-mounting the drives using fstab or systemd you and create a simple script to mount / spin-up the drives, on startup, one by one with a slight delay in-betwen.