3 ms·

btrfs does have some advantages over zfs - no data duplicated between page cache and arc - no upgrade problems on rolling distros - balance allows res

btrfs does have some advantages over zfs - no data duplicated between page cache and arc - no upgrade problems on rolling distros - balance allows restructuring the array - offline dedup, no need for huge dedup tables - ability to turn off checksumming for specific files - O_DIRECT support - reflink copy - fiemap - easy to resize

baaym 5y ago
And even included in the kernel
nix23 5y ago
But the main thing of an fs is to preserve your files...btrfs can't even check the most important point.
- the8472 5y ago
  The checksumming helps to spot faulty hardware, that's a step above most other filesystems and often smart info too.
  - akvadrako 5y ago
    Checksums don't help against bugs. You are much less likely to lose your whole disk with ext4 or ZFS than BTRFS.
- edgyquant 5y ago
  I see this a lot but have never had problems with BTRFS and I’ve used it both on my larger disks (2+tb) and my root (250gb ssd) across multiple computers for the last four years.
chasil 5y ago
- defragmentation
tomatocracy 5y ago
Some of these are fair points but zfsonlinux/OpenZFS has had O_DIRECT since 0.8.x.
- tobias3 5y ago
  ZFSOnLinux just ignores the O_DIRECT flag if I remember correctly. Granted, this is what btrfs should do by default as well since there is an ugly issue where software can modify the O_DIRECT buffer after it was submitted causing btrfs checksum errors even though nothing was corrupted (and there is nothing to be done about it except disabling O_DIRECT or creating a buffer copy).
  - tomatocracy 5y ago
    Yes (and as you mention this is the right thing to do) but I think it means that the Linux kernel will bypass the page cache which is still useful.
curt15 5y ago
>- ability to turn off checksumming for specific files This is something that has always confused me. BTRFS users are always advised to disable copy-on-write (thus preventing checksumming or compression) for VM images or database files to avoid massive performance hits from fragmentation. Even Facebook still stores its databases mostly on XFS filesystems. However, the ZFS community seems to indicate that you can achieve reasonable performance for databases and VMs just by tuning the recordsize (e.g. https://pg.uptrace.dev/zfs/ https://pg.uptrace.dev/zfs/). How does ZFS mitigate the problems from fragmentation?

baaym 5y ago

And even included in the kernel

nix23 5y ago

But the main thing of an fs is to preserve your files...btrfs can't even check the most important point.

the8472 5y ago
The checksumming helps to spot faulty hardware, that's a step above most other filesystems and often smart info too.
- akvadrako 5y ago
  Checksums don't help against bugs. You are much less likely to lose your whole disk with ext4 or ZFS than BTRFS.
edgyquant 5y ago
I see this a lot but have never had problems with BTRFS and I’ve used it both on my larger disks (2+tb) and my root (250gb ssd) across multiple computers for the last four years.

chasil 5y ago

- defragmentation

tomatocracy 5y ago

Some of these are fair points but zfsonlinux/OpenZFS has had O_DIRECT since 0.8.x.

tobias3 5y ago
ZFSOnLinux just ignores the O_DIRECT flag if I remember correctly. Granted, this is what btrfs should do by default as well since there is an ugly issue where software can modify the O_DIRECT buffer after it was submitted causing btrfs checksum errors even though nothing was corrupted (and there is nothing to be done about it except disabling O_DIRECT or creating a buffer copy).
- tomatocracy 5y ago
  Yes (and as you mention this is the right thing to do) but I think it means that the Linux kernel will bypass the page cache which is still useful.

curt15 5y ago

>- ability to turn off checksumming for specific files This is something that has always confused me. BTRFS users are always advised to disable copy-on-write (thus preventing checksumming or compression) for VM images or database files to avoid massive performance hits from fragmentation. Even Facebook still stores its databases mostly on XFS filesystems. However, the ZFS community seems to indicate that you can achieve reasonable performance for databases and VMs just by tuning the recordsize (e.g. https://pg.uptrace.dev/zfs/ https://pg.uptrace.dev/zfs/). How does ZFS mitigate the problems from fragmentation?