Freebsd: Home Nas, Part 1 – Configuring Zfs Mirror (raid1)

Is your desktop or laptop using ECC? For data that you are actively modifying the time that it spends on non-ECC RAM on the server is trivial compared to your desktop or laptop.

I'll take ZFS without ECC over hardware RAID with ECC any day.

other filesystems are just as susceptible to data corruption from memory errors. this is not a weakness unique to ZFS.

"I think people would love more posts about FreeBSD" Translate to: "I would love more post..."

You express a desire for more FreeBSD posts and then immediately wade into all the typical flame-warring that surrounds most BSD/ZFS posts (systemd, ECC RAM), and it's been that way for over a decade at this point.

oh, i didnt knew the concept is taken from Solaris, which version of Solaris? and is there any official source that indicates it is from Solaris?

Sounds a lot like the A/B update method used widely in Android and to a lesser extend for embedded GNU/Linux OTA updates. But it uses two distinct boot partitions. Since ZFS is involved here, I assume that boot environments take advantage of its copy-on-write mechanism to avoid duplicating the entire boot dataset.

NixOS and Guix use a concept called 'system generations' to do the same without the support of the filesystem. LibOSTree can do the same and is called 'atomic rollback'.

Talking about NixOS, does anybody know of a similar concept in the BSD world (preferably FreeBSD)?

Best feature of freebsd. I have really messed up the system and successfully restored a boot environment snapshot and everything is fine after.

It happens by default with freebsd-update (I hope the new pkg replacement still does it too)

Boot environments saved my ass many a time in the last few years. One of my favorite features!

Boot environments are awesome but it’s worth reading up on what is _not_ included in the snapshot. It’s really only the ”base system” and a rollback will keep whatever is in /var, /home and many other directories, so it’s good to know what to expect.

I use ZFSBootMenu with Linux and in that setup, the entire root dataset is in the snapshot, so it’s a ”complete” restore.

I would add these to the list:

- https://is.gd/BECTL

- https://vermaden.wordpress.com/2025/11/25/zfs-boot-environme...

I found thst ZFS to be very simple to understand, everything is controlled by just two commands. Datasets are huge win over partitions which seem like such a weird relic of the past once you have tried datasets. Fairly confident you can grasp ZFS in a hour or 2, you can even make a zfs pool from files to mess around with.

IMHO, there's not much hassle anymore, unless you seek it out. The FreeBSD installer will install to zfs just as well as ufs.

Backups using zfs snapshots are pretty nice; you can pretty easily do incremental updates. zfs scrub is great to have. FreeBSD UFS also has snapshots, but doesn't have a mechanism to check data integrity: fsck checks for well formed metadata only. I don't think ext4 has snapshots or data integrity checking, but I haven't looked at it much.

There are articles and people claiming you need ECC to run zfs or that you need an unreasonable amount of memory. ECC is nice to have, but unnecessary; and you only really need a large amount of ram if you run with deduplication enabled, but very few use cases benefit from deduplication, so the better advice is to ensure you don't enable dedup. I wouldn't necessarily run zfs on something with actually small memory like a router, but then those usually have a specialized flash filesystem and limited writes anyway.

The biggest advantage of ZFS from a operational experience, is that when you have problems, ZFS tells you why. Checksum errors? Something wrong with the hard drive or SATA/SAS cables. Is the disk slow, zfs events will tell you that it spent more than 5 seconds to read sector x from disk /dev/sdf. The zfs cli commands are super-intuitive, and makes fully sense. Compared to ie. virsh, which is just weird to manage vm's.

It definitely worth the hassle. But if everything works fine for you now, don't bother. ZFS is not going away and you can learn it later.

zfs is the furthest thing from hassle, really trivial to use and manage. you'll sit down to do some kind of unhinged change to your infrastructure and it will end up taking 3 command line commands that complete instantly and then you will think, "huh, that was easy" and go back to the rest of your life

Its not a replacement for a physically seperate backup, so putting stuff in the cloud is good (though I'm sure it will get expensive, depending on how much you store).

I use SnapRAID for replication personally, because I like the flexibility it gives in terms of drives that make up the array, I like that it does not work the drives too hard, I like that I can drop drives in over time (to try and lessen coinciding failures) and I like that it works on top of a normal file/folder hierarchy on normal partitions (so I can access the files without SnapRAID should I need to). The cost is that I can lose up to the last day's worth of files (because the parity file is only updated nightly).

I'd avoid hardware RAID controllers when using ZFS, unless you can put it into "IT" mode or equivalent.

> It has a hardware raid1 enclosure, with 2TB formatted as ext4, and the really important stuff is sent to the cloud every night. Should I honestly bother learning zfs...?

It depends on whether you’re interested in it or not. There are multiple benefits with ZFS over your current setup, such as snapshotting, compression and the fact that it’s a virtual volume manager similar to LVM, ie more control over the things I just mentioned on a subset of the storage.

I also avoid hardware raid controllers like the plague for the simple reason that you are then ”vendor locked”, which you wouldn’t be with ZFS, you could easily move the disk(s) to another chassi.

If you are interested in keeping backups, including the ability to go back in time to recover accidentally deleted/changed files, then ZFS with its reliable snapshot facility is fantastic. Other file systems offer some version of this, e.g. btrfs, but they don't have the same reliability as ZFS.

Snapshots on ZFS are extremely cheap, since it works on the block level, so snapshots every hour or even 15 minutes are now doable if you so wish. Combine with weekly or monthly snapshots that can be replicated off-site, and you have a pretty robust storage system.

This is all home sysadmin stuff to be sure, but even if you just use it as a plain filesystem, the checksum integrity guarantees are worth the price of admission IMO.

FWIW, software RAID like ZFS mirrors or mdm is often superior to hardware raid especially for home use. If your raid controller goes blooey, which does happen, unless you have the exact same controller to replace it, you run a chance of not being able to mount your drives. Even very basic computers are fast enough to saturate the drives in software these days.

> Is zfs really worth the hassle

Yes. Also: what hazzle? It's in many ways simpler than alternatives.

> Is zfs really worth the hassle, for someone who does not have time to play "home sysadmin" more than once or twice a year?

I'd argue that it's better for minimizing sysadmin work than the alternatives. Running a scrub, replacing a disk, taking a snapshot, restoring a snapshot, sending a snapshot somewhere (read: trivial incremental backups), etc. are all one command, and it's easy to work with.

> I've just rebuilt my little home server (mostly for samba, plus a little bit of docker for kids to play with). It has a hardware raid1 enclosure, with 2TB formatted as ext4, and the really important stuff is sent to the cloud every night. Should I honestly bother learning zfs...? I see it popping up more and more but I just can't see the benefits for occasional use.

The reason I personally would prefer it in that situation is that I don't really trust the layers under the filesystem to protect data from corruption or even to notice when it's corrupted. If you're sufficiently confident that your hardware RAID1 will always store data correctly and never mess it up, then it's close enough. (I wouldn't trust it, but that's me.) At that point, the only benefit I see to ZFS would be snapshots; an incremental `zfs send` is more efficient than however else you're syncing to the cloud.

Learning effort aside, there’s also the ZFS hardware requirements issue. I bought a four bay NAS couple years ago and looked into TrueNAS. I (somewhat) remember coming across details such as ZFS benefitting from larger amounts of ECC RAM and higher number of drives than what I had. This post covers details about different types of caches and resource requirements:

https://www.45drives.com/community/articles/zfs-caching/

> can't see the benefits for occasional use

I've lost work and personal data to bit rot in NAS filesystems before. Archived VM images wouldn't boot anymore after months in storage. Multiple vacation photos became colorful static part way through on disk due to a bit flip in the middle of the JPEG stream. I've had zero issues since switching to ZFS (even without ECC.)

Another huge benefit of ZFS is the copy-on-write (CoW) snapshots, which saved me many times as an IT administrator. It was effortless to restore files when users accidentally deleted them, and recovering from a cryptolocker type attack is also instant. Without CoW, snapshots are possible, but they're expensive and slow. I saw a 20-user office try to snapshots on their 30TB Windows Server NAS hoping to avoid having to revert to tape backups to recover the occasional accidentally deleted file. While hourly snapshots would have been ideal, the NAS only had room for only two snapshots, and would crawl to a halt while it created them. But ZFS's performance won't suffer if you snapshot every minute.

When it's time to backup, ZFS' send/recv capability means you only ever move the differences when backing up, and they're pre-computed so you don't have to re-index an entire volume to determine that you only need to move 124KB, making small transfers are lightning fast. Once backup completes, you have verified that the snapshot on both sides is bit-for-bit identical. While this is the essential property of a backup, most filesystems cannot guarantee it.

ZFS has become a hard requirement for any storage system I build/buy.

Depending on exactly what you are looking for, maybe search for raid levels, like raid0, raidz?

  "RAID" site:news.ycombinator.com

TrueNAS scale is, TrueNAS core is still FreeBSD (legacy, but it's still there)

With the metadata stuff they added you could put metadata on nvme and keep the spinning rust. All flash is nice though but not as economical as this.