One SSD and one HDD

TrueNAS General
1

Apart from not being able to use RAID levels, are there any disadvantages to using only 1 HDD for data storage? (I would run TrueNAS on a separate SSD)

2

Not really. I’m not sure that basic of a system would be a good fit for TrueNAS, but there’s no real harm that would result from it, other than increased risk to your data.

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3

It will work, but of course I’d only really recommend it for data you’ve got no problem possibly losing. TrueNAS / ZFS is primarily focused on data protection, after all.

If you do this, what you can do in the future is grab another HDD and then convert your pool into a mirror for some redundancy.

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4

Thanks for the answers

5

And you can still enjoy automatic repair of in-drive corruption by setting copies=2. Of course, this costs half the capacity and protects from sector errors but not from complete drive failure.

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There are multiple benefits for using ZFS on a single device:

  • Automatic compression
  • Possible encryption of datasets or whole pools
  • Ability to use copies=2 on just selected dataset(s), allowing single copies for everything else, (like media that might be available in backups). Not possible with 2 disk Mirror.
  • And even without copies=2, you get 2 copies of metadata by default. So any failing copy of metadata can be both supplied to the user as needed. Then automatically correct to failing copy.
  • Last, regular ZFS scrubs should always be run on single disk pools, (or even striped pools). This allows ZFS to tell the user which files are lost, so they can be restored individually. This is important when dealing with >1TB of data, like media.

So yes, single disk or striped ZFS pools have their place.

In fact, I use such in my miniature media server. It has 1 x 1TB mSATA SSD and 1 x 2TB 2.5" HDD. I carve out a portion on each for the OS, and use a ZFS mirror. But, I use a stripe of both devices remaining storage for my media. (Because I have multiple backups.)

I have even lost dozens of files over the 9 years I have used it. Simple for me to fetch the current backup disk and restore it. (Backup disk is also ZFS so I will know if the backup of the file for the restore is bad…)

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