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Btrfs Allocator Hints

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Re: Btrfs Allocator Hints

#31

Post by ChocolateGod »

sandreas wrote: post #17

Well, first of all: I'm not trying to bash BTRFS at all, it probably is just not meant for me. However, I'm trying to gain information it is really considered stable (like rock solid) or it might have been a hardware Problem on my system. I used cryptsetup with BTRFS because I encrypt all of my stuff. One day, the system froze and after reboot the partition was unrecoverably gone (the whole story[1]). Not a real prob…

I've used it as my desktops main filesystem for many years and not had any problems. I have regular snapshots with snapper. I run the latest kernel, so ZFS is not an option.

That said, I avoid it like the plague on servers, to get acceptable performance (or avoid fragmentation) with VMs or databases you need to disable COW which disables many of it's features, so it's better just to roll with XFS (and get pseudo-snapshots anyway).

Re: Btrfs Allocator Hints

#32

Post by BlimpSpike »

pa7ch wrote: post #21
sandreas wrote: post #17

Well, first of all: I'm not trying to bash BTRFS at all, it probably is just not meant for me. However, I'm trying to gain information it is really considered stable (like rock solid) or it might have been a hardware Problem on my system. I used cryptsetup with BTRFS because I encrypt all of my stuff. One day, the system froze and after reboot the partition was unrecoverably gone (the whole story[1]). Not a real prob…

I worked on a linux distro some years ago that had to pull btrfs long after people had started saying thats its truly solid because customers had so many issues. Its probably improved since but its hard to know. Im surprised fedora workstation defaults to it now. I'm hoping bcachefs finds its way in the next few years as being the rock solid fs it aims to be.

I hadn't heard of bcachefs, but I looked it up and apparently Linus just removed it from the kernel source tree last month for non-technical reasons.

https://en.wikipedia.org/wiki/Bcachefs#History

Re: Btrfs Allocator Hints

#33

Post by gavinsyancey »

sandreas wrote: post #17

Well, first of all: I'm not trying to bash BTRFS at all, it probably is just not meant for me. However, I'm trying to gain information it is really considered stable (like rock solid) or it might have been a hardware Problem on my system. I used cryptsetup with BTRFS because I encrypt all of my stuff. One day, the system froze and after reboot the partition was unrecoverably gone (the whole story[1]). Not a real prob…

My btrfs filesystem has been slowly eating my data for a while; large files will find their first 128k replaced with all nulls. Rewriting it will sometimes fix it temporarily, but it'll revert back to all nulls after some time. That said, this might be my fault for using raid6 for data and trying to replace a failing disk a while ago.

Re: Btrfs Allocator Hints

#34

Post by koverstreet »

BlimpSpike wrote: post #32
pa7ch wrote: post #21

Earlier quoted context omitted.

I worked on a linux distro some years ago that had to pull btrfs long after people had started saying thats its truly solid because customers had so many issues. Its probably improved since but its hard to know. Im surprised fedora workstation defaults to it now. I'm hoping bcachefs finds its way in the next few years as being the rock solid fs it aims to be.

I hadn't heard of bcachefs, but I looked it up and apparently Linus just removed it from the kernel source tree last month for non-technical reasons. https://en.wikipedia.org/wiki/Bcachefs#History

He hasn't, yet, but it's anyone's guess what's he's going to do.

Regardless, development isn't going to stop, we may just have to switch to shipping as a DKMS module. And considering the issues we've had with getting bugfixes out that might have been the better way all along.

Re: Btrfs Allocator Hints

#35

Post by homebrewer »

sandreas wrote: post #24
fpoling wrote: post #22

Earlier quoted context omitted.

Have you used 4K sectors with cryptsetup? Many distributions still defaults to 512 bytes if SSD reports 512 bytes as its logical size and with 512 sectors there are heavier load on the system. I was reluctant to use BTRFS on my Linux laptop but for the last 3 years I have been using it with 4K cryptsetup with no issues.

I used the default archinstall... did not check the sector size, but good to hear it works for you. Maybe I'll check again with my next setup.

FWIW, basically all of arch linux' infrastructure has been running on top of btrfs for several years, and last time I asked them, they didn't have any more problems with it than with any other filesystem.

https://gitlab.archlinux.org/archlinux/infrastructure

Re: Btrfs Allocator Hints

#36

Post by homebrewer »

gavinsyancey wrote: post #33
sandreas wrote: post #17

Well, first of all: I'm not trying to bash BTRFS at all, it probably is just not meant for me. However, I'm trying to gain information it is really considered stable (like rock solid) or it might have been a hardware Problem on my system. I used cryptsetup with BTRFS because I encrypt all of my stuff. One day, the system froze and after reboot the partition was unrecoverably gone (the whole story[1]). Not a real prob…

My btrfs filesystem has been slowly eating my data for a while; large files will find their first 128k replaced with all nulls. Rewriting it will sometimes fix it temporarily, but it'll revert back to all nulls after some time. That said, this might be my fault for using raid6 for data and trying to replace a failing disk a while ago.

raid 5/6 is completely broken and there's not much interest in fixing it — nobody who's willing to pay for its development (which includes Facebook, SUSE, Oracle, and WD) uses raid 5/6; you shouldn't have been running it in the first place. I understand it's basically blaming the victim, but doing at least some research on the filesystem before starting to use it is a good idea in any case.

https://btrfs.readthedocs.io/en/latest/Status.html

edit: just checked, it says the same thing in man pages — not for production use, testing/development only.

Re: Btrfs Allocator Hints

#37

Post by homebrewer »

ChocolateGod wrote: post #31
sandreas wrote: post #17

Well, first of all: I'm not trying to bash BTRFS at all, it probably is just not meant for me. However, I'm trying to gain information it is really considered stable (like rock solid) or it might have been a hardware Problem on my system. I used cryptsetup with BTRFS because I encrypt all of my stuff. One day, the system froze and after reboot the partition was unrecoverably gone (the whole story[1]). Not a real prob…

I've used it as my desktops main filesystem for many years and not had any problems. I have regular snapshots with snapper. I run the latest kernel, so ZFS is not an option. That said, I avoid it like the plague on servers, to get acceptable performance (or avoid fragmentation) with VMs or databases you need to disable COW which disables many of it's features, so it's better just to roll with XFS (and get pseudo-snap…

In the unlikely case you're running SQLite, it's possible to get okay performance on btrfs too:

https://wiki.tnonline.net/w/Blog/SQLite_Performance_on_Btrfs

Re: Btrfs Allocator Hints

#38

Post by koverstreet »

ajross wrote: post #13
bayindirh wrote: post #12

Earlier quoted context omitted.

Actually, it doesn't work like that. Sun's ZFS7420 had a terabyte of RAM per controller , and these work in tandem, and after a certain pressure, the thing can't keep up even though it also uses specialized SSDs to reduce HDD array access during requests, and these were blazingly fast boxes for their time. When you drive a couple thousand physical nodes with a some-petabytes sized volumes, no amount of RAM can save y…

> When you drive a couple thousand physical nodes with a some-petabytes sized volumes You aren't doing that with ZFS or btrfs, though. Datacenter-scale storage solutions (c.f. Lustre, which you mention) have long since abandoned traditional filesystem techniques like the one in the linked article. And they rely almost exclusively on RAM behavior for their performance characteristics, not the underlying storage (which…

Besides ZFS (and I've heard of exabyte sized ZFS filesystems), bcachefs is absolutely capable of petabyte sized filesystems.

Re: Btrfs Allocator Hints

#39

Post by amy214 »

ghostly_s wrote: post #18
sandreas wrote: post #17

Well, first of all: I'm not trying to bash BTRFS at all, it probably is just not meant for me. However, I'm trying to gain information it is really considered stable (like rock solid) or it might have been a hardware Problem on my system. I used cryptsetup with BTRFS because I encrypt all of my stuff. One day, the system froze and after reboot the partition was unrecoverably gone (the whole story[1]). Not a real prob…

Yes, my story with btrfs is quite similar- used it for a couple years, suddenly threw some undocumented error and refused to mount, asked about it on the dev irc channel and was told apparently it was a known issue with no solution, have fun rebuilding from backups. No suggestion that anyone was interested in documenting this issue, let alone fixing it. These same people are the only ones in the world suggesting btrf…

I ran it on opensuse and it would 100% lock out a core on some sort of crontab tree structure rebalancing (?) .. I mean.. hello? online algorithm? Dynamic rebalancing? scheduled FS restructuring, really? ReiserFS dancing trees from 20 years ago? If thats how they think, "meh, the user just has to deal", no wonder this is how they handle bugs.

Re: Btrfs Allocator Hints

#40

Post by theamk »

riku_iki wrote: post #28
sandreas wrote: post #27

Earlier quoted context omitted.

Thank you for your opinion. Well... it did not just fail. Cryptsetup mounted everything fine, but the BTRFS tools did not find a valid filesystem on it. While it could have been a bit flip that destroyed the whole encryption layer, BTRFS debugging revealed that there was some traces of BTRFS headers after mounting cryptsetup and some of the data on the decrypted partition was there... This probably means the encrypti…

> Well, maybe it was my fault but since I'm using the exact same system with the same hardware right now (same NVMe SSD), I really doubt that. anecdotes could be exchanged in both directions: I run heavy data processing with max possible throughput on top of btrfs raid for 10 years already, and never had any data loss. I am absolutely certain if you expect data integrity while relying on single disk: it is your fault…

The reliability is about variety of workloads, not amount of data or throughput. It's easy to write a filesystem which works well in the ideal case, it's the bad or unusual traffic patters which cause problem. For all that I know maybe that btrfs complete failure was because of kernel crash caused by bad USB hardware. Or there was a cosmic ray hitting memory chip.

But you know who's fault is it? It's btrfs's one. Other filesystems don't lose entire volumes that easily.

Over time, I've abused ext4 (and ext3) in all sorts of ways: override random sector, mount twice (via loop so kernel's double-mount detector did not work), use bad SATA hardware which introduced bit errors.. There was some data loss, and sometimes I had to manually sort though tens of thousands of files in "lost+found" but I did not lose the entire filesystem.

I only saw the "entire partition loss" only happened to me when we tried btrfs. It was a part of ceph cluster so no actual data was lost.. but as you may guess we did not use btrfs ever again.

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