6 ms·

I think the biggest missing feature for home/casual use in XFS right now is shrinking. Currently, it's impossible to reduce an XFS filesystem (partition) in siz

I think the biggest missing feature for home/casual use in XFS right now is shrinking. Currently, it's impossible to reduce an XFS filesystem (partition) in size, so you have to commit to your disk layout once you've set it up. Whether it's to install another OS side-by-side, grow a swap partition, experiment with or gradually migrate to another filesystem, none are currently possible without adding additional physical storage or using loop devices. The same applies to ZFS (it's not possible to shrink a ZFS pool), which is why I'm currently using btrfs (with all its pain points) on my machines.

saghm 9y ago
Doesn't LVM solve this? I know this might not work as well in some cases with multi-disk arrays, but I'm not sure I'd call that "casual use".
- CyberShadow 9y ago
  You mean, by overcommitting the filesystem size, and using discard to free up underlying space? Possibly... how well does that work in practice? What happens when LVM runs out of space due to some runaway disk-filling process, is the filesystem ready to handle out-of-space errors coming from LVM in all situations?
jbronn 9y ago
From operations experience, the risks of data loss with btrfs far outweigh volume shrinking capabilities on either XFS or ZFS.
- CyberShadow 9y ago
  Fortunately, btrfs is really good at backups. Well, so is ZFS, but in some situations, like choosing what filesystem to use on a rented dedicated server, any choice that could lead to a situation requiring physical hardware configuration changes is a non-starter. ZFS licensing is an issue too, as it means that you can't just boot into any ol' Linux live CD (or remotely boot into a rescue environment) to fix the system or salvage the data on it.
  - deleted 9y ago
    [deleted]
  - e12e 9y ago
    > Fortunately, btrfs is really good at backups. For backing up to another file system? How so? Is there something like "zfs send" or even "xfsdump"? Honest question - I haven't look that closely at btrfs.
    - Vogtinator 9y ago
      Yes, "btrfs send" and "receive" exist for that purpose.
      - chungy 9y ago
        Mind that it doesn't work quite so well as ZFS: btrfs send/receive doesn't produce an identical file system as the source. ctimes aren't preserved, some attributes, and depending on mount options, ACLs and xattrs can vanish too.
  - laumars 9y ago
    > ZFS licensing is an issue too, as it means that you can't just boot into any ol' Linux live CD (or remotely boot into a rescue environment) to fix the system or salvage the data on it. Sure you can. I've done just this with 3 different live CDs: ArchLinux, FreeBSD and OpenSolaris. I'm fairly sure I've also used ZFS on the Ubuntu Desktop live CD as well but that was just for playing rather than rescusing a degraded system.
    - vetinari 9y ago
      FreeBSD and OpenSolaris probably aren't very useful, when trying to rescue a Linux system. Especially if you need to chroot and run things from there. (My need so far was to rescue non-booting system, because the zfs package upgrade went wrong and didn't update spl too. Re-running dracut would be a somewhat problematic from these two systems). Ubuntu desktop live CD doesn't contain zfs, you have to install it from apt. However, if you have a ZFS system, I see no problem with having an USB stick with minimal installation of your distro of choice, together with ZFS support. I'm glad I did have it since the ZFS install.
- muxator 9y ago
  I really would like more data about it. My impression is that the biggest limitation that btrfs suffers nowadays is a severely lacking communication. Even the official wiki is not so up to date, and there are a lot of horror stories surviving from years ago. The situation has been quite reliable for some time now (single disk, raid{0,1,10}), moreover the feature set of btrfs is really wide (on par with zfs), with a very high flexibility: you can mix and match disks of different capacities, shrink and expand pools, change their redundance level through filtering, everything can be done online...
  - nisa 9y ago
    Even it it doesn't break your filesystem anymore: Performance is subpar in all aspects except sequential read/write even compared to ZFS. high snapshot count degrades performance and lot's of gotchas you discover after using it for a while. RAID1 is not RAID1 - it's oddness of the pid decides which disk to read from... scrub impacts io massivly. Tooling and documentation is not exactly great... lot's of quirky hacks to make up for design errors IMHO. If it works for you, fine. Also it appears to get better - I won't touch it anymore if I can avoid it.
- DCKing 9y ago
  Is there really any reason to believe that Btrfs has more risk of data loss than XFS or ZFS, at least on simple single or mirrored drives? Honest question - my home box runs a Btrfs mirror on openSUSE.
  - iforgotpassword 9y ago
    The two most obvious reasons to assume so are that btrfs is in comparison relatively new and quite complex. Not to say zfs isn't complex, but I'd rather trust zfs just because of its age. That being said, unless I really need those specific features, I go for ext4 whenever possible, as it has to be the most battle tested one, at least when it comes to *nix. It also seems that fsck.ext4 has almost magical powers sometimes, but that shouldn't stop you from making backups obviously. Related: http://events.linuxfoundation.org/sites/events/files/slides/AFL%20filesystem%20fuzzing%2C%20Vault%202016_0.pdf http://events.linuxfoundation.org/sites/events/files/slides/...
bobdole1234 9y ago
Since XFS works by multiple allocation groups spread across the volume, that would require you to migrate data out of the area you want to reclaim, which would require a pretty significant reshuffle of the volume contents. It's easier to just backup and refill with a single set of reads and single set of writes than it is to suffer the huge overhead of all that random metadata updating and seeking.
unixhero 9y ago
No, the biggest missing is native compression.
- pmlnr 9y ago
  There are 3 filesystems that can do transparent compression: NTFS, ZFS, btrfs. One is for Windows, the other isn't available for RedHat/CentOS, the third is getting sunset. XFS could really benefit from compression support.
  - unixhero 9y ago
    Btrfs isn't getting sunset tho. And ZFS can be installed on any Linux distribution.
    - vetinari 9y ago
      GP probably meant in RHEL/CentOS. It was deprecated in 7.4, it will be removed in 7.5 (already is in beta). Yeah, I spent one afternoon migrating a CentOS+btrfs machine to XFS.
  - vetinari 9y ago
    ZFS is available in RHEL/CentOS. Not as a first-party option, but thanks to kABI that Red Hat provides, it is provided by the ZoL project also in a form of a binary kernel module, ready to go, without having to fumble around with DKMS and compilers. Btrfs is being obsoleted by RHEL only, because they have XFS expertise, but not Btrfs. No need to split limited resources. Other distributions will continue with development. SuSE doesn't intend to stop.
- fh973 9y ago
  Which file types are there that benefit from compression, but are not yet compressed as part of the format?
  - vetinari 9y ago
    The general mix has some potential for compression. Looking at one machine available: * / has 2.08 compression ratio, * /var/cache 2.15 * /var/tmp 1.0 * /home 1.02 * /srv 1.10 (few web apps, pgsql instance for these web apps, svn repo, samba shares, local prometheus store). If your server uses spinning rust, you can also increase the I/O by using compression. You are trading the CPU time for I/O bandwidth. Depending on your workload, it may be a sensible trade-off.
josteink 9y ago
> I think the biggest missing feature for home/casual use in XFS right now is shrinking. .... The same applies to ZFS (it's not possible to shrink a ZFS pool) I have to admit that recently I've only had the exact opposite use-case: Wanting to expand volumes. Except for authoring install-media or images where you want to reduce the final file-size... What common use-cases are there for volume-reductions?

saghm 9y ago

Doesn't LVM solve this? I know this might not work as well in some cases with multi-disk arrays, but I'm not sure I'd call that "casual use".

CyberShadow 9y ago
You mean, by overcommitting the filesystem size, and using discard to free up underlying space? Possibly... how well does that work in practice? What happens when LVM runs out of space due to some runaway disk-filling process, is the filesystem ready to handle out-of-space errors coming from LVM in all situations?

jbronn 9y ago

From operations experience, the risks of data loss with btrfs far outweigh volume shrinking capabilities on either XFS or ZFS.

CyberShadow 9y ago
Fortunately, btrfs is really good at backups. Well, so is ZFS, but in some situations, like choosing what filesystem to use on a rented dedicated server, any choice that could lead to a situation requiring physical hardware configuration changes is a non-starter. ZFS licensing is an issue too, as it means that you can't just boot into any ol' Linux live CD (or remotely boot into a rescue environment) to fix the system or salvage the data on it.
- deleted 9y ago
  [deleted]
- e12e 9y ago
  > Fortunately, btrfs is really good at backups. For backing up to another file system? How so? Is there something like "zfs send" or even "xfsdump"? Honest question - I haven't look that closely at btrfs.
  - Vogtinator 9y ago
    Yes, "btrfs send" and "receive" exist for that purpose.
    - chungy 9y ago
      Mind that it doesn't work quite so well as ZFS: btrfs send/receive doesn't produce an identical file system as the source. ctimes aren't preserved, some attributes, and depending on mount options, ACLs and xattrs can vanish too.
- laumars 9y ago
  > ZFS licensing is an issue too, as it means that you can't just boot into any ol' Linux live CD (or remotely boot into a rescue environment) to fix the system or salvage the data on it. Sure you can. I've done just this with 3 different live CDs: ArchLinux, FreeBSD and OpenSolaris. I'm fairly sure I've also used ZFS on the Ubuntu Desktop live CD as well but that was just for playing rather than rescusing a degraded system.
  - vetinari 9y ago
    FreeBSD and OpenSolaris probably aren't very useful, when trying to rescue a Linux system. Especially if you need to chroot and run things from there. (My need so far was to rescue non-booting system, because the zfs package upgrade went wrong and didn't update spl too. Re-running dracut would be a somewhat problematic from these two systems). Ubuntu desktop live CD doesn't contain zfs, you have to install it from apt. However, if you have a ZFS system, I see no problem with having an USB stick with minimal installation of your distro of choice, together with ZFS support. I'm glad I did have it since the ZFS install.
muxator 9y ago
I really would like more data about it. My impression is that the biggest limitation that btrfs suffers nowadays is a severely lacking communication. Even the official wiki is not so up to date, and there are a lot of horror stories surviving from years ago. The situation has been quite reliable for some time now (single disk, raid{0,1,10}), moreover the feature set of btrfs is really wide (on par with zfs), with a very high flexibility: you can mix and match disks of different capacities, shrink and expand pools, change their redundance level through filtering, everything can be done online...
- nisa 9y ago
  Even it it doesn't break your filesystem anymore: Performance is subpar in all aspects except sequential read/write even compared to ZFS. high snapshot count degrades performance and lot's of gotchas you discover after using it for a while. RAID1 is not RAID1 - it's oddness of the pid decides which disk to read from... scrub impacts io massivly. Tooling and documentation is not exactly great... lot's of quirky hacks to make up for design errors IMHO. If it works for you, fine. Also it appears to get better - I won't touch it anymore if I can avoid it.
DCKing 9y ago
Is there really any reason to believe that Btrfs has more risk of data loss than XFS or ZFS, at least on simple single or mirrored drives? Honest question - my home box runs a Btrfs mirror on openSUSE.
- iforgotpassword 9y ago
  The two most obvious reasons to assume so are that btrfs is in comparison relatively new and quite complex. Not to say zfs isn't complex, but I'd rather trust zfs just because of its age. That being said, unless I really need those specific features, I go for ext4 whenever possible, as it has to be the most battle tested one, at least when it comes to *nix. It also seems that fsck.ext4 has almost magical powers sometimes, but that shouldn't stop you from making backups obviously. Related: http://events.linuxfoundation.org/sites/events/files/slides/AFL%20filesystem%20fuzzing%2C%20Vault%202016_0.pdf http://events.linuxfoundation.org/sites/events/files/slides/...

bobdole1234 9y ago

Since XFS works by multiple allocation groups spread across the volume, that would require you to migrate data out of the area you want to reclaim, which would require a pretty significant reshuffle of the volume contents. It's easier to just backup and refill with a single set of reads and single set of writes than it is to suffer the huge overhead of all that random metadata updating and seeking.

unixhero 9y ago

No, the biggest missing is native compression.

pmlnr 9y ago
There are 3 filesystems that can do transparent compression: NTFS, ZFS, btrfs. One is for Windows, the other isn't available for RedHat/CentOS, the third is getting sunset. XFS could really benefit from compression support.
- unixhero 9y ago
  Btrfs isn't getting sunset tho. And ZFS can be installed on any Linux distribution.
  - vetinari 9y ago
    GP probably meant in RHEL/CentOS. It was deprecated in 7.4, it will be removed in 7.5 (already is in beta). Yeah, I spent one afternoon migrating a CentOS+btrfs machine to XFS.
- vetinari 9y ago
  ZFS is available in RHEL/CentOS. Not as a first-party option, but thanks to kABI that Red Hat provides, it is provided by the ZoL project also in a form of a binary kernel module, ready to go, without having to fumble around with DKMS and compilers. Btrfs is being obsoleted by RHEL only, because they have XFS expertise, but not Btrfs. No need to split limited resources. Other distributions will continue with development. SuSE doesn't intend to stop.
fh973 9y ago
Which file types are there that benefit from compression, but are not yet compressed as part of the format?
- vetinari 9y ago
  The general mix has some potential for compression. Looking at one machine available: * / has 2.08 compression ratio, * /var/cache 2.15 * /var/tmp 1.0 * /home 1.02 * /srv 1.10 (few web apps, pgsql instance for these web apps, svn repo, samba shares, local prometheus store). If your server uses spinning rust, you can also increase the I/O by using compression. You are trading the CPU time for I/O bandwidth. Depending on your workload, it may be a sensible trade-off.

josteink 9y ago

> I think the biggest missing feature for home/casual use in XFS right now is shrinking. .... The same applies to ZFS (it's not possible to shrink a ZFS pool) I have to admit that recently I've only had the exact opposite use-case: Wanting to expand volumes. Except for authoring install-media or images where you want to reduce the final file-size... What common use-cases are there for volume-reductions?