Individual disk standby / hibernation possible per pool in TrueNAS Mini?

[ByteMan]

Hi!
Based on research on this forum, I understand that it is possible to get disk hibernation to work on a TrueNAS Mini unit as long as it is ensured that the disks are not being accessed by background tasks, plugins, etc.
I plan on having the following disk setup in a Mini X or X+:
1x RAIDz1 (2x 4TB SSDs) - I would host anything that TrueNAS needs to access frequently on here, e.g. iocage
1x three disk RAID5 OR four disk RAID6 (14TB HDDs)

The idea behind this setup was:
- To have a noiseless SSD pool for frequent access of files, on-demand without wait times for drives to spin up
- HDD volume to be used as semi-cold storage pool for less frequently accessed files (accessed 5-10 times per week).

Is it possible to automatically have the HDDs power down (hibernate) when not in use, while still allowing regular access to the SSD volume?
Likewise (assuming all drives are already in hibernation), I was hoping the HDDs would not spin up when only the SSDs are accessed?

Will this setup work as intended?

 

[jgreco]

Neither ZFS nor the Mini's support RAID5 or RAID6. And RAIDZ1 requires more than two disks.

Perhaps you meant something else?

Pools do not interact with each other. There is no reason that accesses to one pool would "wake up" hibernated drives for another pool. As you note, you do need to make sure there's nothing bothering the disks.

 

[ByteMan]

Apologies for the incorrect terminology.
Disk setup with corrected terminology:
1x mirror vdev (2x 4TB SSDs)
1x three disk RAIDZ1 OR four disk RAIDZ2 (14TB HDDs)

Pools do not interact with each other. There is no reason that accesses to one pool would "wake up" hibernated drives for another pool.

This is good news, thank you!
Just to confirm, this should be the same with any standard supported hardware platform (e.g. ASRock Rack MB)?

 

[jgreco]

I don't see what that would have to do with anything. It IS possible for a platform to have trouble hibernating disks, but that's not going to be dependent on accesses to the other pool. It is also possible to burn out an undersized PSU with the spinup current requirements. Because hibernating disks is generally a bad idea, almost no one here on the forums does it, so there isn't a lot of information available.

 

[ByteMan]

Because hibernating disks is generally a bad idea, almost no one here on the forums does it, so there isn't a lot of information available.

I understand and I see why it is advised against in most use cases, but would you still recommend for me to have my drives running 24/7 even when I only access them as little as 5 times in a week?

 

[jgreco]

If we assume that "as little as 5" were to mean "maybe an average of 10", that works out to 520 starts/stops a year, or 2600 over a five year lifespan. That's not an intolerably large number of load/unloads, but it's pretty common to see a 24/7 HDD blow past 50K hours without all the start/stops.

It is kind of like the difference between city driving and freeway driving for a car. Perhaps counterintuitively, freeway miles are easier on vehicles, just because you're not exercising various other parts of the car in stressy ways. Keeping the miles rolling with the engine at that freeway speed sweet spot and no braking is lower wear.

 

[ByteMan]

I reached out to ixsystems support and this is what they stated in regards to disk hibernation on the TrueNAS Mini:

a disk hibernation feature is generally incompatible with the zfs file system as it can cause a hibernating disk to register as "failed" when it's actually just asleep

Would you know if this is documented officially somewhere?

 

[jgreco]

Would you know if this is documented officially somewhere?

I would say you have the official word in the quoted e-mail.

Additionally, if you search for the word "hibernation" in these forums, I would expect it likely that virtually every such instance is followed up by someone admonishing the poster not to do it.

This includes indirect concerns such as drive spinup current as discussed in the power supply sizing guide.

If you are looking for the ZFS equivalent of a McDonald's style "Contents may be extremely hot" official warning on their coffee cups, no, I don't think there is any such thing for sleeping disks on ZFS.

The community believes that spinning down disks is a bad thing. You're certainly allowed to try to do it if you please. In my opinion, the riskiest aspect is if you've improperly sized your PSU and it cannot handle a dozen simultaneous spinups, and you smoke your PSU.

In response to the iX email, I don't recall having seen spun down disks reported as failed. In general, ZFS hangs for a reasonable time waiting for I/O to complete, so that's vaguely eyebrow-raising, but iXsystems has a ton of systems out there, and I'm sure they've seen it all.

At the end of the day, you can do as you please. Just don't expect a lot of help from the forum. AFAIK, none of the regulars here do this.

 

[Samuel Tai]

If your goal is to save power, there are other ways of doing it with 24x7 spinning disks. See this impromptu inventory of some very low power systems at https://www.truenas.com/community/t...e-power-consumption-hw-recommendations.96992/.