this post was submitted on 25 May 2026
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I currently have a secondary pool (with raidz2) that I was originally going to use for my important documents, such as storage for Paperless-ngx, as raidz offers corruption detection and repair. The pool is encrypted.

However, I'm concerned about rebuild times (it's a pool of 4 22TB drives). Is btrfs a better choice for this use case, or should I just go with raidz like I originally planned?

Edit: I should have mentioned that I already have 4-3-2 backups configured - I'm primarily interested in the "self-healing" aspect of ZFS so that I don't have to recover from backups unless necessary, and to resolve corruption on the fly without me having to notice that a file is corrupt.

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[–] EpicFailGuy@lemmy.world 1 points 1 day ago

BTRFS is not production ready (by their own admission)

1 disk redundancy leaves you exposed whenever you have to rebuild ... has significantly higer chances of having a second disk fail so you should use double redundancy. Raid z2 doesn't make sense because with raid z10 you get performance gains AND double redundancy.

Go with raid z10

[–] felbane@lemmy.world 25 points 5 days ago* (last edited 5 days ago) (2 children)

RAID is not a backup.

RAID is not for data safety.

RAID is for:

  1. Ensuring availability of data in the face of hardware failure. That means your files don't disappear when a drive dies and you have some time to swap out for functional hardware and restore redundancy.
  2. Presenting multiple drives as one larger unit. This is what striping does, and to a lesser extent the parity-mode levels.
  3. Improving performance (sometimes). A RAID mirror is generally much faster to read from than any individual drive because reads can be interleaved across drive members. A stripe can be much faster because writes are distributed across drive members. This is less of a bonus today with solid state/nvme drives, but it's still applicable to spinning rust.

If your concern is protecting your data, set up a 3-2-1 backup strategy.

[–] zyberwoof@lemmy.world 1 points 2 days ago (1 children)

RAID is not a backup.

True

RAID is not for data safety.

Not true.

  • RAID helps prevent data loss in the event that a drive failure occurs before changes are replicated to backups. If you upload photos and then delete them from your camera, they will likely be stored in just one location for a period of time. If you have a drive failure without RAID, you could lose your only copy.
  • With ZFS, RAID can be used to protect against things like bitrot. Even data at rest can become corrupt over time. ZFS stores checksums of the files to know if corruption occurs. And with one or more parity drives, ZFS can automatically repair the corruption when detected. Without this, detecting and fixing these kinds of issues can be much more difficult.

I'm in 100% agreement that RAID is not essential, and that backups are a much higher priority. In fact, without backups in place, I'm not generally in favor of RAID. RAID adds additional complexity. That complexity can result in data loss. Especially due to user error. But once backups are part of the equation, RAID can add additional layers of security for your data.

[–] felbane@lemmy.world 1 points 2 days ago

Yes, valid points that I didn't really want to muddy the discussion with. In my experience, most people hear the Redundant in RAID and think that's sufficient and that their data is safe. Maybe poor choice of words on my part, but that's what I meant re: "data safety."

You're fully correct that a proper RAID setup can provide additional layers of availability atop a robust backup process, but I'd wager most of the people who are interested in that extra layer are already aware of the limitations of RAID.

I do run RAIDZ1 on my franken-nas due to limited drive sizes on that machine, the goal being to maximize usable space while providing a sufficient amount of time to address a drive failure. If drive prices ever become reasonable again, I'll likely rebuild the system with 6-8 drives in a RAIDZ2 configuration just for a little more peace of mind, but as long as my off-site backups are running, I sleep at night just fine.

[–] CorrectAlias@piefed.blahaj.zone 2 points 4 days ago* (last edited 4 days ago)

I'm very aware and have full 4-3-2 backups already. I'm also not interested in a standard raid. Thanks though! It's always good to mention that raid is not a backup. I simply want to add more protection from disk corruption (not necessarily full failure) so that I don't need to recover from backups unless I absolutely must. A benefit would also be resolving corruption before I even notice it.

[–] gblues@lemmy.zip 1 points 3 days ago

I have been enjoying using ZFS, although it's a not a killer filesystem for every scenario, I think it would be the best solution for you. also, you can try the "free consulting" on the 2.5 Admins podcast (show@2.5admins.com). Jim and Allen are ZFS lovely weirdos, but they can explain better why would be ZFS a better solution for your case. Give it a try. I have done it before and really helped me.

[–] tal@lemmy.today 12 points 5 days ago* (last edited 5 days ago)

I was originally going to use for my important documents

Not quite what you're asking, but if your concern is avoiding data loss, if you haven't already, I'd set up a backup before I started setting up a RAID or similar setup.

[–] ikidd@lemmy.dbzer0.com 7 points 4 days ago

Don't use any btrfs raid levels besides mirroring. There are long-standing raid bugs that they wontfix in 5 and 6 that have led to data loss.

[–] i078@europe.pub 9 points 5 days ago (1 children)

While redundancy in a drive setup helps, it’s not really a backup and thus not a “safe” way to store important information on it’s own.

That said, selecting the way you setup a raid system is based on risk and utility. I have a raid1 with a hotspare for important files. And use raid5 with 3&4 drives for less important stuff. You can also optimise for reading speed for example (as the same file can be drawn from multiple drives)

[–] chris@l.roofo.cc 4 points 5 days ago (1 children)

Like you said: RAID is not a backup. If it's import follow at least the 3-2-1 rule. 3 copies on at least 2 different media, 1 of them off site.

[–] CorrectAlias@piefed.blahaj.zone 2 points 4 days ago* (last edited 4 days ago)

Absolutely, 4-3-2 is what I use now! MDisc backups have been great.

[–] xrun_detected@programming.dev 7 points 5 days ago (1 children)

I'd stay on zfs, I simply don't trust btrfs’ raid implementation. For very important documents I also set copies=2 (or 3) on that dataset, just in case.

And as others already said: 3-2-1 backups ;)

Yeah, I'm leaning towards ZFS for sure after reading about btrfs' past..

[–] oats@piefed.zip 6 points 5 days ago (2 children)

Filesystem doesn't really matter once you have a reliable, redundant off-site backup and recovery plan set up and tested.

Really, use what fs feels best for you. And do your backups.

Did I mention backups are important?

[–] NotEasyBeingGreen@slrpnk.net 1 points 3 days ago

I prefer file systems that checksum data. Without this it is difficult to know when there has been corruption. I generally use brtfs for this reason.

I should have mentioned that I was (and still am) using XFS for my primary pool. XFS has been great, I was just hoping for a solution which would make it so I don't have to hit my backups unless absolutely necessary (such as full array loss, for example). ZFS' data corruption protection is very intriguing, it's mostly the rebuild time and write speed that is making me think about doing something else.

[–] pedroapero@lemmy.ml 4 points 4 days ago* (last edited 4 days ago)

I've been using a raid1 btrfs pool to store offline backups for around 10 years. It's 4 rotating drives (2x4TB+2x12TB). I replaced / rebalanced 3 disks with larger / newer ones already (went fine). I identified a bad usb/sata controller, and lots of bitrots on one old disk (scrub was able to correct a few thousands errors).

I'm getting around 80MB/s read/write throughput (not great but OK for offline backup). I'm able to mount it on low-powered / low-memory devices (not the case for ZFS). Scrub takes around 2 days IIRC (for around 10TB of actual data), so I run it once a year.

I keep it simple and thus am not using advanced features (dedup / encryption / snapshots / subvolumes / raid5/6/10). So far its a good match for my needs.

[–] MangoPenguin@piefed.social 3 points 5 days ago (1 children)

What about 2 mirrored pools of 2 drives each, then back up the main pool to the other with either ZFS snapshots or a tool like Restic.

Ideally you also need an offsite backup of important files too, but that gets you part way to a robust system that can handle corruption or accidental deletions.

[–] CorrectAlias@piefed.blahaj.zone 1 points 4 days ago* (last edited 4 days ago)

Would this just be to help with the rebuild time? Raid10 in ZFS is an interesting idea, which would also require two mirrors and striping.

[–] ruuster13@lemmy.zip 2 points 4 days ago

If rebuild time is truly your main concern, you could configure the 4 drives as raid 1+0. On truenas I think it would be called a pool of 2 mirror vdevs. It would give you much faster rebuild time and still have 1-2 drive failure tolerance.

[–] tychosmoose@piefed.social 3 points 5 days ago (1 children)

For your situation I would be more likely to go with a single drive with btrfs and dup for metadata redundancy. Regular snapshots and scrubs.

Use a second drive in the same system with btrfs to store snapshots at wider scheduled intervals. These will be bigger since no CoW on the separate file system. Scheduled scrub here too.

Use a third drive with ext4 as a backup target using a separate backup mechanism.

Use the fourth drive as a spare, or in a separate location as a target to send the backups if you don't already have an off-site solution.

Interesting idea.

[–] exu@feditown.com 3 points 5 days ago (2 children)

Maybe you could switch to a raid10 (mirrored striped vdevs) for faster rebuild time.

BTRFS is relatively similar to ZFS when it comes to their raid implementation, though using raid5 or raid6 comes with some caveats.

[–] felbane@lemmy.world 7 points 5 days ago* (last edited 5 days ago)

I would absolutely not trust BTRFS's implementation. Maybe things are better now but it earned the backronym Bro The RAID Fuckin Sucks for a reason.

[–] CorrectAlias@piefed.blahaj.zone 1 points 4 days ago (1 children)

Raid 10 is and interesting idea for sure. It would certainly help with write speeds, although if I want to utilize the "self-healing" of ZFS, I'd need to do two (separately striped) vdevs that mirror each other to get the equivalent to RAID10, right?

[–] exu@feditown.com 2 points 4 days ago

You'd create two mirror vdevs in the same zpool to get the raid 10 equivalent

[–] homik@slrpnk.net 1 points 4 days ago

If you're storing, then offline, read only, checksummed and preferably encrypted. And above all, several tested backups. I'm partial to making erofs images from dirs, but any archive that fits the content type works.

For the random access cache on top, whatever.

[–] Decronym@lemmy.decronym.xyz 1 points 5 days ago* (last edited 1 day ago) (1 children)

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

Fewer Letters More Letters
HTTP Hypertext Transfer Protocol, the Web
IP Internet Protocol
RAID Redundant Array of Independent Disks for mass storage
SSL Secure Sockets Layer, for transparent encryption
TLS Transport Layer Security, supersedes SSL
VPN Virtual Private Network
ZFS Solaris/Linux filesystem focusing on data integrity
nginx Popular HTTP server

6 acronyms in this thread; the most compressed thread commented on today has 9 acronyms.

[Thread #314 for this comm, first seen 25th May 2026, 11:10] [FAQ] [Full list] [Contact] [Source code]

[–] Blue_Morpho@lemmy.world -1 points 5 days ago (2 children)

Why was this upvoted? It's AI slop giving definitions for acronyms that aren't in this thread and not even related to backups.

[–] Zeoic@lemmy.world 5 points 5 days ago (1 children)

It isn't AI, you can take a look at the source code for it from the url it provides. Obviously the detection needs some tweaking, but extra acronyms in the list doesn’t really hurt anything when the other half are relevant.

[–] Blue_Morpho@lemmy.world 2 points 4 days ago* (last edited 4 days ago) (1 children)

Detection is completely broken because it finds terms that aren't anywhere in the thread, even as substrings.

AI isn't just LLM.

[–] Zeoic@lemmy.world 2 points 4 days ago (1 children)

It wasnt even LLMs until the public took the term and changed it lol. Unless you are calling every algorithim ever made AI these days, this isnt AI.

[–] Blue_Morpho@lemmy.world 1 points 4 days ago (1 children)

Chess programs were AI. Expert systems which were regular logic were AI. Lisp was an AI language. Chat bots were AI.

This is a bot which makes it a type of AI and it's really inaccurate.

[–] Zeoic@lemmy.world 1 points 4 days ago (2 children)

uhm, no? Literally none of that was considered AI. Even chatbots, people weren't calling them AI until LLMs came around and were stuck in them. Lisp is a language USED for AI research, that doesn't make it AI itself.

This bot is most definitely not even close to what people consider AI

[–] meltedcheese@c.im 1 points 4 days ago (1 children)

@Zeoic You are both correct. Chess was chosen as an early problem domain for work on first-order logic-based programming. That certainly was considered AI. People really interested in chess later abandoned logic programming in favor of brute-force, highly parallel special purpose hardware. That was not AI.

“Expert systems” (I hate that term) are application area of “Pattern-Directed Inference Systems” (PDIS). Rule-based systems are just one type of PDIS. For example, “Constraint Satisfaction” is another powerful AI technique often used in resource optimization and scheduling systems.

[–] Blue_Morpho@lemmy.world 1 points 4 days ago

You are both correct That certainly was considered AI.

Notice my use of past tense as well as Zeoic use of past tense. I said chess was AI as you stated. Zeoic denied that chess was ever AI.

[–] Blue_Morpho@lemmy.world 1 points 4 days ago (1 children)

https://www.chessprogramming.org/Artificial_Intelligence

" the term 'artificial intelligence' was coined by John McCarthy in the proposal for the 1956 Dartmouth Conference [4] . In its beginning, Computer Chess was called the Drosophila of Artificial Intelligence. "

Expert Systems:

https://en.wikipedia.org/wiki/Expert_system "In artificial intelligence (AI), an expert system is a computer system emulating the decision-making ability of a human expert.[1] "

Chatbots in AI:

https://liacademy.co.uk/the-story-of-eliza-the-ai-that-fooled-the-world/

https://en.wikipedia.org/wiki/Eugene_Goostman

Lisp is a language USED for AI research, that doesn’t make it AI itself. "Lisp was an AI language."

I didn't say Lisp was AI. I said it was a language used for AI.

[–] meltedcheese@c.im 1 points 4 days ago

@Blue_Morpho @selfhosted Thanks for posting this. Some interesting articles that I didn’t know about. The Wikipedia article on expert systems needs some work. Apart from editing, the content is fine but incomplete, and the citations are not the best. I may take a crack at contributing, or I might take a nap. The 80s-90s were my prime years as a developer of intelligent systems, including but not limited to knowledge based expert systems. One of the most successful AI tools I co-invented was SHINE, still in use today.

https://en.wikipedia.org/wiki/SHINE/_Expert/_System

[–] homik@slrpnk.net 2 points 4 days ago* (last edited 4 days ago)

At least this time it has a few terms that people might not know. Usually it just spasms obvious trivialities.