ZFS SSD power usage / sleep modes

I’m considering building a home NAS. I plan to make an all-flash NAS for three reasons:

  1. Spinning rust can’t keep up with the IOPS demand (~2000 iops) of the cryptocurrency full nodes I’ll run on it with the number of disks I’d be using (2-4).
  2. I don’t need huge capacity (10TB ideal size)
  3. I hate, hate, HATE waiting for HDDs to spin up after being idle. I did it for 6 years…I’m done waiting.

My question is one I don’t have the hardware to test for myself at the moment: How does ZFS handle putting drives in lower power states when they aren’t being used? Let’s assume that I sequester the cryptocurrency usage to one non-ZFS ssd, and that the majority of the NAS’s time will be spent idle, with brief periods of activity. One of the main advantages of SSDs is that they can go to sleep and wake up in milliseconds. Does ZFS leverage this, or would the drives stay at full ‘idle’ power, instead of going to sleep while not in use?

When I had a hardware RAID card I could configure the spin-down time. Actually, even in Windows I can still do that. I don’t see that option with SSDs, and my google-fu isn’t turning up anything of use. I know if the pool is constantly being read from (99% of the crypto node activity is random reads) it won’t put the disks to sleep because they’re always in use. Hence why I was planning to put the blockchain data on its own device.

I would not worry about leaving flash drives on, they idle at only a few watts. Simply switching to Flash would have a large up front cost, that the ongoing power cost is real low. Power on time is less of an issue for flash drives, and even when busy, heat is only really an issue for the controller, and only really when it’s busy?

I had a ZFS drive in a USB caddy which liked to power down. Normally the system would be fine, but sometimes the system would need a response from the drive, which could not spin back up to respond quick enough, so sometimes the drive would be marked Degraded, and might have brought down the pool.

I would recommend letting the system choose when to idle the drives.
Leaving them on is quicker to get back to work, does not cause much wear at all, and barely costs much in electricity.

A shelf of spinning hard drives on the other hand, there you could save…

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