I'm considering building a NAS and I'm evaluating my options. Power consumption is quite important for a server that is always on. Just to give you some context, these are the options I'm considering:

  1. Raspberry Pi with a USB hub and external hard drives
  2. Retired gaming PC with internal hard drives
  3. Save myself time and effort and pay a cloud provider

The gaming PC is definitely not low power and keeping it always on is not an option. The primary purpose is to use it for backups, so if I can configure it to Wake-On-LAN and hibernate after a short period of inactivity, it could be an option.

I think the peak power consumption of my old Raspberry Pi is about 1W. The power consumption of the hard drives depends on what I end up buying, but it seems like it typically ranges from 2W to 10W, and I'll probably get somewhen between 3 to 6 drives. That means that power consumption for the drives would be somewhere between 6W and 60W. Being able to control when the disks are sleeping could have a big impact on the power consumption of the NAS.

Some external hard drives/docking stations/enclosures advertise that they have a sleep mode. One said that the disk would sleep after 10 minutes of inactivity for instance. It also seems like some manufacturers provide drivers that allow you to configure the time before the disk sleeps.

What I haven't found any proof of (yet?), is that there are external hard drives that allow the OS to decide when a drive should sleep. Does that exist? If so, what is required for that to work?


Yes. You can control power settings on hard drives and even issue ATA commands to standby/sleep on demand. hdparm is a useful utility on Linux to accomplish this. From the hdparm man page:

hdparm provides a command line interface to various kernel interfaces supported by the Linux SATA/PATA/SAS "libata" subsystem and the older IDE driver subsystem. Many newer (2008 and later) USB drive enclosures now also support "SAT" (SCSI-ATA Command Translation) and therefore may also work with hdparm. Eg. recent WD "Passport" models and recent NexStar-3 enclosures. Some options may work correctly only with the latest kernels.

The Arch Linux wiki has some great documentation on it:

While this is for Arch Linux, systemd and hdparm still apply to Raspberry Pi OS.


Windows includes this as an option under advanced power settings:

Windows 10 advanced power options


Most modern NASes will include disk power-saving settings out of the box too. For example, Netgear:

Netgear NAS disk spin-down options

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  • Thank you, that is very helpful. What confuses me is the marketing. The product description doesn't say anything about SAT or SCSI-ATA Command Translation. I haven't found a single one that explicitly mentions this. What is sometimes mentioned is a sleep mode, which doesn't really make sense if the disk sleeping is controlled by the OS anyway. It looks to me like I will have to buy, try, return, repeat, until I find one that works, or is this more or less standard on all enclosures now? Is this somehow related to UASP, by the way? – Erik B Jul 14 at 19:45

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