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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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
What kind of disks, and how is your ZFS set up? Something seems amis here.
Raid 5/6, only bcachefs will solve it
Btrfs Raid 5 and raid 6 are unstable and dangerous
Bcachefs is cool but it is way to new and isn’t even part of the kernel as of yet.
https://en.wikipedia.org/wiki/Bcachefs it was added as of Linux 6.7
Edit: and I’ve said raid 5/6 as what troubles btrfs have so you proved my point while trying to explain to me that I’m not right
I though was then removed later as there was a disagreement between Linus and the bcachefs dev
Yeah, i remember something like that, i don’t remember exactly which kernel version it was when they removed it
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.
When did this happen?
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
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
When did this happen?
I think 5 years ago, on Ubuntu
ACID go brrr
You shouldn’t have abysmal performance with ZFS. Something must be up.
What’s up is ZFS. It is solid but the architecture is very dated at this point.
There are about a hundred different settings I could try to change but at some point it is easier to go btrfs where it works out of the box.
What seems dated in its architecture? Last time I looked at it, it struck me as pretty modern compared to what’s in use today.
It doesn’t share well. Anytime anything IO heavy happens the system completely locks up.
That doesn’t happen on other systems
That doesn’t speak much of the architecture. Also it’s really odd. Not denying what you’re seeing is happening, just that it seems odd based on the setups I run with ZFS. My main server is in fact a shared machine that I use as a workstation and games along as a server. All works in parallel. I used to have a mirror, then a 4-disk RAIDz and now an 8-disk RAIDz2. I have multiple applications constantly using the pool. I don’t notice any performance slowdowns on the desktop, or in-game when IO goes high. The only time I notice anything is when something like multiple Plex transcoders hit the CPU hard. Sequential performance is around 1.3GB/s which is limited by the data bus speeds (USB DAS boxes). Random performance is very good although I don’t have any numbers out of my head. I’m using mostly WD Elements shucked disks and a couple of IronWolfs. No enterprise grade disks on this system.
I’m also not saying that you have to keep fucking around with it instead of going Btrfs. Simply adding another anecdote to the picture. If I had a serious problem like that and couldn’t figure it out I’d be on LVMRAID+Ext4 which is what used prior to ZFS.
Yeah maybe my machines are cursed
That is totally possible. I spent a month changing boards and CPUs to fix a curse on my main, unrelated to storage. In case you’re curious.
@avidamoeba @possiblylinux127 Does your ZFS not print on Tuesdays? https://bugs.launchpad.net/ubuntu/+source/cupsys/+bug/255161/
Since most people with decently simple setups don’t have the described problem likely somethings up with your setup.
Yes ifta old and yes it’s complicated but it doesn’t have to be to get a decent performance.
I have been trying to get ZFS working well for months. Also I am not the only one having issues as I have seen lots of other posts about similar problems.
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.
Was that less than 2 years ago? Were you using kernel 5.15 or newer?
Yes that was may/june 23 and I was on a 6.x kernel
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.
With version 2.3 (currently in RC), ZFS will at least support RAIDZ expansion. That should already help a lot for a NAS usecase.
Btrfs Raid 10 reportedly is stable
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
I’ve got raid 6 at the base level and LVM for partitioning and ext4 filesystem for a k8s setup. Based on this, btrfs doesn’t provide me with any advantages that I don’t already have at a lower level.
Additionaly, for my system, btrfs uses more bits per file or something such that I was running out of disk space vs ext4. Yeah, I can go buy more disks, but I like to think that I’m running at peak efficiency, using all the bits, with no waste.
I have no problem running it with raid 5/6. The important thing is to have a UPS.
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.
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.
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.
I have never heard of anyone getting those speeds without dedicated high end hardware
Also the write will always be your bottleneck.
This is an old PC (Intel i7 3770K) with 2 HDDs (16 TB) attached to onboard SATA3 controller, 16 GB RAM and 1 SSD (120 GB). Nothing special. And it’s quite busy because it’s my home server with a VM and containers.
I’m seeing very similar speeds on my two-HDD RAID1. The computer has an AMD 8500G CPU but the load from ZFS is minimal. Reading / writing a 50GB /dev/urandom file (larger than the cache) gives me:
- 169 MB/s write
- 254 MB/s read
What’s your setup?
Maybe I am CPU bottlenecked. I have a mix of i5-8500 and i7-6700k
The drives are a mix but I get almost the same performance across machines
It’s possible, but you should be able to see it quite easily. In my case, the CPU utilization was very low, so the same test should also not be CPU-bottlenecked on your system.
Is your machine part of a cluster by chance? Of so, when you do a VM transfer what performance do you see?
I have similar speeds on a truenas that I installed on a simple i3 8100
How much ram and what is the drive size?
I suspect this also could be an issue with SSDs. I have seen a lot a posts around describing similar performance on SSDs.
64 gb of ecc ram (48gb cache used by zfs) with 2tb drives (3 of them)
Yeah it sounds like I don’t have enough ram.
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.
Proxmox only supports btrfs or ZFS
Or at least that’s what I thought
ext4 and others too.
For raid?
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?
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.
You can ignore the RAM usage, it’s just cache. It uses up to half your RAM by default but if other things need it zfs will just clear RAM for that to happen.
Btrfs only has issues with raid 5. Works well for raid 1 and 0. No reason to change if it works for you
It is stable with raid 0,1 and 10.
Raid 5 and 6 are dangerous
Do you rely on snapshotting and journaling? If so backup your snapshots.
Why?
I already take backups but I’m curious if you have had any serious issues
Are you backing up files from the FS or sre you backing up the snapshots? I had a corrupted journal from a power outage that borked my install. Could not get to the snapshots on boot. Booted into a live disk and recovered the snapshot that way. Would’ve taken hours to restore from a standard backup, however it was minutes restoring the snapshot.
If you’re not backing up BTRFS snapshots and just backing up files you’re better off just using ext4.
