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About a year ago I switched to ZFS for Proxmox so that I wouldn't be running technology preview.

Btrfs gave me no issues for years and I even replaced a dying disk with no issues. I use raid 1 for my Proxmox machines. Anyway I moved to ZFS and it has been a less that ideal experience. The separate kernel modules mean that I can't downgrade the kernel plus the performance on my hardware is abysmal. I get only like 50-100mb/s vs the several hundred I would get with btrfs.

Any reason I shouldn't go back to btrfs? There seems to be a community fear of btrfs eating data or having unexplainable errors. That is sad to hear as btrfs has had lots of time to mature in the last 8 years. I would never have considered it 5-6 years ago but now it seems like a solid choice.

Anyone else pondering or using btrfs? It seems like a solid choice.

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[–] [email protected] 4 points 2 hours ago

Btrfs came default with my new Synology, where I have it in Synology's raid config (similar to raid 1 I think) and I haven't had any problems.

I don't recommend the btrfs drivers for windows 10. I had a drive using this and it would often become unreachable under load, but this is more a Windows problem than a problem with btrfs

[–] [email protected] 2 points 3 hours ago

What kind of disks, and how is your ZFS set up? Something seems amis here.

[–] [email protected] 1 points 3 hours ago

I am using btrfs on raid1 for a few years now and no major issue.

It's a bit annoying that a system with a degraded raid doesn't boot up without manual intervention though.

Also, not sure why but I recently broke a system installation on btrfs by taking out the drive and accessing it (and writing to it) from another PC via an USB adapter. But I guess that is not a common scenario.

[–] [email protected] 11 points 7 hours ago

Did you set the correct block size for your disk? Especially modern SSDs like to pretend they have 512B sectors for some compatibility reason, while the hardware can only do 4k sectors. Make sure to set ashift=12.

Proxmox also uses a very small volblocksize by default. This mostly applies to RAIDz, but try using a higher value like 64k. (Default on Proxmox is 8k or 16k on newer versions)

https://discourse.practicalzfs.com/t/psa-raidz2-proxmox-efficiency-performance/1694

[–] [email protected] 2 points 5 hours ago (1 children)

My setup is different to yours but not totally different. I run ESXi 8, and I started to use BTRFS on some of my VM's.

I had a power failure, that was longer than the UPS could handle. Most of the system shutdown safely, a few VM's did not. All of the EXT4 VM's were easily recovered (including another one that was XFS). TWO of the BTRFS systems crashed into a non recoverable state.

Nothing I could do to fix them, they were just toast. I had no choice but to recover using backups. This made me highly aware that BTRFS is still not a reliable FS.

I am migrating everything from BTRFS to something more stable and reliable like EXT4. It's simply not worth the headache.

[–] [email protected] 1 points 4 hours ago

When did this happen?

[–] [email protected] 27 points 10 hours ago (2 children)

Don't use btrfs if you need RAID 5 or 6.

The RAID56 feature provides striping and parity over several devices, same as the traditional RAID5/6. There are some implementation and design deficiencies that make it unreliable for some corner cases and the feature should not be used in production, only for evaluation or testing. The power failure safety for metadata with RAID56 is not 100%.

https://btrfs.readthedocs.io/en/latest/btrfs-man5.html#raid56-status-and-recommended-practices

[–] [email protected] 2 points 1 hour ago (1 children)

I have no problem running it with raid 5/6. The important thing is to have a UPS.

[–] [email protected] 1 points 4 minutes ago

I've been running a btrfs storage array with data on raid5 and metadata I believe raid1 for the last 5 or so years and have yet to have a problem because of it. I did unfortunately learn not to fully trust the windows btrfs driver but was fortunately able to restore from backups and redownloading.

I wouldn't hesitate to set it up again for myself or anybody else, and adding a UPS would be icing on the cake. (I added UPS to my setup this last summer)

[–] [email protected] 6 points 5 hours ago

Or run the raid 5 or 6 separately, with hardware raid or mdadm

Even for simple mirroring there's an argument to be made for running it separately from btrfs using mdadm. You do lose the benefit of btrfs being able to automatically pick the valid copy on localised corruption, but the admin tools are easier to use and more proven in a case of full disk failure, and if you run an encrypted block device you need to encrypt half as much stuff.

[–] [email protected] 0 points 3 hours ago

Raid 5/6, only bcachefs will solve it

[–] [email protected] 15 points 9 hours ago (2 children)

You shouldn't have abysmal performance with ZFS. Something must be up.

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[–] [email protected] 39 points 12 hours ago (4 children)

A bit of topic; am I the only one that pronounces it "butterface"?

[–] [email protected] 4 points 2 hours ago (1 children)

Isn't it meant to be like "better FS"? So you're not too far off.

[–] [email protected] 2 points 1 hour ago

i call it "butter FS"

[–] [email protected] 0 points 3 hours ago

Similarly, I read bcachefs as BCA Chefs 😅

[–] [email protected] 42 points 12 hours ago (1 children)
[–] [email protected] 30 points 12 hours ago

You son of a bitch, I'm in.

[–] [email protected] 17 points 11 hours ago

Ah feck. Not any more.

[–] [email protected] 6 points 9 hours ago (2 children)

One day I had a power outage and I wasn't able to mount the btrfs system disk anymore. I could mount it in another Linux but I wasn't able to boot from it anymore. I was very pissed, lost a whole day of work

[–] [email protected] 3 points 4 hours ago (1 children)
[–] [email protected] 2 points 2 hours ago

I think 5 years ago, on Ubuntu

[–] [email protected] 2 points 7 hours ago

ACID go brrr

[–] [email protected] 28 points 13 hours ago (1 children)

No reason not to. Old reputations die hard, but it's been many many years since I've had an issue.

I like also that btrfs is a lot more flexible than ZFS which is pretty strict about the size and number of disks, whereas you can upgrade a btrfs array ad hoc.

I'll add to avoid RAID5/6 as that is still not considered safe, but you mentioned RAID1 which has no issues.

[–] [email protected] 2 points 12 hours ago (2 children)

I've been vaguely planning on using btrfs in raid5 for my next storage upgrade. Is it really so bad?

[–] [email protected] 1 points 4 hours ago

It's affected by the write-hole phenomenon. In BTRFS case that can mean that perfectly good old data might corrupt without any notice.

[–] [email protected] 7 points 11 hours ago

Check status here. It looks like it may be a little better than the past, but I'm not sure I'd trust it.

An alternative approach I use is mergerfs + snapraid + snapraid-btrfs. This isn't the best idea for a system drive, but if it's something like a NAS it works well and snapraid-btrfs doesn't have the write hole issues that normal snapraid does since it operates on r/o snapshots instead of raw data.

[–] [email protected] 8 points 10 hours ago (2 children)

I've been using single-disk btrfs for my rootfs on every system for almost a decade. Great for snapshots while still being an in-tree driver. I also like being able to use subvolumes to treat / and /home (maybe others) similar to separate filesystems without actually being different partitions.

I had used it for my NAS array too, with btrfs raid1 (on top of luks), but migrated that over to ZFS a couple years ago because I wanted to get more usable storage space for the same money. btrfs raid5 is widely reported to be flawed and seemed to be in purgatory of never being fixed, so I moved to raidz1 instead.

One thing I miss is heterogenous arrays: with btrfs I can gradually upgrade my storage one disk at a time (without rewriting the filesystem) and it uses all of my space. For example, two 12TB drives, two 8TB drives, and one 4TB drive adds up to 44TB and raid1 cuts that in half to 22TB effective space. ZFS doesn't do that. Before I could migrate to ZFS I had to commit to buying a bunch of new drives (5x12TB not counting the backup array) so that every drive is the same size and I felt confident it would be enough space to last me a long time since growing it after the fact is a burden.

[–] [email protected] 2 points 9 hours ago

With version 2.3 (currently in RC), ZFS will at least support RAIDZ expansion. That should already help a lot for a NAS usecase.

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[–] [email protected] 5 points 10 hours ago (1 children)

One time I had a power outage and one of the btrfs hds (not in a raid) couldn't be read anymore after reboot. Even with help from the (official) btrfs mailinglist It was impossible to repair the file system. After a lot of low level tinkering I was able to retrieve the files, but the file system itself was absolutely broken, no repair process was possible. I since switched to zfs, the emergency options are much more capable.

[–] [email protected] 3 points 9 hours ago (1 children)

Was that less than 2 years ago? Were you using kernel 5.15 or newer?

[–] [email protected] 3 points 3 hours ago

Yes that was may/june 23 and I was on a 6.x kernel

[–] [email protected] 5 points 11 hours ago (8 children)

The question is how do you get a bad performance with ZFS?

I just tried to read a large file and it gave me uncached 280 MB/s from two mirrored HDDs.

The fourth run (obviously cached) gave me over 3.8 GB/s.

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[–] [email protected] 3 points 10 hours ago

Not proxmox-specific, but I've been using btrfs on my servers and laptops for the past 6 years with zero issues. The only times it's bugged out is due to bad hardware, and having the filesystem shouting at me to make me aware of that was fantastic.

The only place I don't use zfs is for my nas data drives (since I want raidz2, and btrfs raid5 is hella shady) but the nas rootfs is btrfs.

[–] [email protected] 5 points 13 hours ago

If it didn't give you problems, go for it. I've run it for years and never had issues either.

[–] [email protected] 2 points 11 hours ago (2 children)

Meh. I run proxmox and other boot drives on ext4, data drives on xfs. I don't have any need for additional features in btrfs. Shrinking would be nice, so maybe someday I'll use ext4 for data too.

I started with zfs instead of RAID, but I found I spent way too much time trying to manage RAM and tuning it, whereas I could just configure RAID 10 once and be done with it. The performance differences are insignificant, since most of the work it does happens in the background.

You can benchmark them if you care about performance. You can find plenty of discussion by googling "ext vs xfs vs btrfs" or whichever ones you're considering. They haven't changed that much in the past few years.

[–] [email protected] 2 points 11 hours ago (1 children)

but I found I spent way too much time trying to manage RAM and tuning it,

I spent none, and it works fine. what was you're issue?

[–] [email protected] 2 points 11 hours ago

I have four 6tb data drives and 32gb of RAM. When I set them up with zfs, it claimed quite a few gb of RAM for its cache. I tried allocating some of the other NVMe drive as cache, and tried to reduce RAM usage to reasonable levels, but like I said, I found that I was spending a lot of time fiddling instead of just configuring RAID and have it running just fine in much less time.

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[–] [email protected] 2 points 12 hours ago (1 children)

Btrfs only has issues with raid 5. Works well for raid 1 and 0. No reason to change if it works for you

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[–] [email protected] 2 points 12 hours ago

Using it here. Love the flexibility and features.

[–] [email protected] 2 points 13 hours ago

I run it now because I wanted to try it. I haven't had any issues. A friend recommended it as a stable option.

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