Feature status on btrfs

SUSE Product Topics SLES Configure-Administer
1

[LIST=1]
[] Is there any documentation as to what features of BTRFS are implemented and supported in SLES11-SP2? Or is it identical to the kernel version (3.0?)
[] Is it planned to backport specific BTRFS-Features from more recent kernels into SLES11-SP2? I’m specifically looking at quota support and/or qgroups.
[/LIST]

I’m starting to set up a new server and if BTRFS won’t support any sort of quotas (via quotad or subvolume) in any plannable time, then I need to reconsider (distribution or just the filesystem).

I found a featurelist in /usr/src/linux/Documentation/filesystems/btrfs.txt but I have no idea if this is in sync with the actual btrfs kernel module.

Additionally, YAST partitioner lets you activate quotas but then fails mounting the volume (because btrfs doesn’t understand quota mount options) - a subsequent call to yast partitioner resulted in a kernel panic.

2

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3

horiba wrote:
[color=blue]

  • Is there any documentation as to what features of BTRFS are
    implemented and supported in SLES11-SP2? Or is it identical to the
    kernel version (3.0?)
  • Is it planned to backport specific BTRFS-Features from more recent
    kernels into SLES11-SP2? I’m specifically looking at quota support
    and/or qgroups.[/color]

Have you seen:
Release Notes for SUSE Linux Enterprise Server 11 Service Pack 2

http://www.novell.com/linux/releasenotes/x86_64/SUSE-SLES/11-SP2/#fate-306585-1

[color=blue]

3.1.1. Support for the btrfs File System

Btrfs is a copy-on-write (CoW) general purpose file system. Based on
the CoW functionality, btrfs provides snapshoting. Beyond that data
and metadata checksums improve the reliability of the file system.
btrfs is highly scalable, but also supports online shrinking to adopt
to real-life environments. On appropriate storage devices btrfs also
supports the TRIM command.

Support

With SUSE Linux Enterprise 11 SP2, the btrfs file system joins ext3,
reiserfs, xfs and ocfs2 as commercially supported file systems. Each
file system offers disctinct advantages. While the installation
default is ext3, we recommend xfs when maximizing data performance is
desired, and btrfs as a root file system when snapshotting and
rollback capabilities are required. Btrfs is supported as a root file
system (i.e. the file system for the operating system) across all
architectures of SUSE Linux Enterprise 11 SP2. Customers are advised
to use the YaST partitioner (or AutoYaST) to build their systems:
YaST will prepare the btrfs file system for use with subvolumes and
snapshots. Snapshots will be automatically enabled for the root file
system using SUSE’s snapper infrastructure. For more information
about snapper, its integration into ZYpp and YaST, and the YaST
snapper module, see the SUSE Linux Enterprise documentation.

Migration from “ext” File Systems to btrfs

Migration from existing “ext” file systems (ext2, ext3, ext4) is
supported “offline” and “in place”. Calling “btrfs-convert [device]”
will convert the file system. This is an offline process, which needs
at least 15% free space on the device, but is applied in place. Roll
back: calling “btrfs-convert -r [device]” will roll back. Caveat:
when rolling back, all data will be lost that has been added after
the conversion into btrfs; in other words: the roll back is complete,
not partial.

RAID

Btrfs is supported on top of MD (multiple devices) and DM (device
mapper) configurations. Please use the YaST partitioner to achieve a
proper setup. Multivolume/RAID with btrfs is not supported yet and
will be enabled with a future maintenance update.

Future Plans

We are planning to announce support for btrfs' built-in multi

volume handling and RAID in a later version of SUSE Linux Enterprise.

Starting with SUSE Linux Enterprise 12, we are planning to

implement bootloader support for /boot on btrfs.

Transparent compression is implemented and mature. We are

planning to support this functionality in the YaST partitioner in a
future release.

We are commited to actively work on the btrfs file system with

the community, and we keep customers and partners informed about
progress and experience in terms of scalability and performance. This
may also apply to cloud and cloud storage infrastructures.

Online Check and Repair Functionality

Check and repair functionality (“scrub”) is available as part of the
btrfs command line tools. “Scrub” is aimed to verify data and
metadata assuming the tree structures are fine. “Scrub” can (and
should) be run periodically on a mounted file system: it runs as a
background process during normal operation.

The tool “fsck.btrfs” tool will soon be available in the SUSE Linux
Enterprise update repositories.

Capacity Planning

If you are planning to use btrfs with its snapshot capability, it is
advisable to reserve twice as much disk space than the standard
storage proposal. This is automatically done by the YaST2 partitioner
for the root file system.

Hard Link Limitation

In order to provide a more robust file system, btrfs incorporates
back references for all file names, eliminating the classic
“lost+found” directory added during recovery. A temporary limitation
of this approach affects the number of hard links in a single
directory that link to the same file. The limitation is dynamic based
on the length of the file names used. A realistic average is
approximately 150 hard links. When using 255 character file names,
the limit is 14 links. We intend to raise the limitation to a more
usable limit of 65535 links in a future maintenance update.

For more information about btrfs, see the SUSE Linux Enterprise 11
documentation.[/color]

–
Kevin Boyle - Knowledge Partner
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4

Hello Mr. Boyle,

Yes, I read through the release Notes. That’s why I came here and asked. Maybe I overestimated “actively working with the community”. I’m sorry for that.

So according to this answer, I just assume this means “No”.

But please consider updating the YaST partitioner to not let the user enable quotas on btrfs. It’s an impossible combination (yet) and could leave (under some circumstances) the system in an unbootable state.

5

horiba wrote:
[color=blue]

Hello Mr. Boyle,

Yes, I read through the release Notes. That’s why I came here and
asked. Maybe I overestimated “actively working with the community”.
I’m sorry for that.

So according to this answer, I just assume this means “No”.[/color]

When people ask questions here, we don’t always know how much research
they may have already done. That is why I referred you to the
documentation.

You must remember that we are volunteers and while we may be active in
the Suse, Novell, and NetIQ forums, we don’t work for these
organisations and therefore don’t always know the internal workings of
a product or what product enhancements may be forthcoming.
[color=blue]

But please consider updating the YaST partitioner to not let the user
enable quotas on btrfs. It’s an impossible combination (yet) and could
leave (under some circumstances) the system in an unbootable state.[/color]

I will pass on your comments and try to have a bug opened. If you
encounter a program defect or a security issue you can open a service
request yourself to have the issue corrected.

–
Kevin Boyle - Knowledge Partner
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show your appreciation and click on the star below…

6

[QUOTE=KBOYLE;10818]horiba wrote:

You must remember that we are volunteers and while we may be active in
the Suse, Novell, and NetIQ forums, we don’t work for these
organisations and therefore don’t always know the internal workings of
a product or what product enhancements may be forthcoming.
[/QUOTE]

I’m sorry again - I didn’t mean to sound aggressive. As btrfs is a moving target, I hoped someone could specify what snapshot is in SLES11SP2 and if that snapshot is going to move in the lifetime of SLES11 (like the kernel did in SP2).

[color=blue]

I would love to send bug reports to SuSE, as service requests are not available for basic subscriptions. But that’s a different discussion. (But please inform me if I overlooked a way to submit bugs outside of service requests)

7

Hi horiba,

have you checked out http://support.novell.com/additional/bugreport.html?sourceidint=suplnav4a_bug ? It feels like kind of a black hole, but trust me, I’ve had responses when submitting there, without a support contract nor any special status. It just isn’t guaranteed that somebody will get in touch with you. And yes, that’s only for defects, not for feature requests.

Regards,
Jens

8

Hello Jens,

thank for the URL - no I wasn’t aware of that. I’ll bookmark that and will try and submit a bug after the holidays.

9

horiba wrote:
[color=blue]

I’m sorry again - I didn’t mean to sound aggressive.[/color]

No need to apologise. I didn’t consider your comments to be at all
aggressive.
[color=blue]

As btrfs is a
moving target, I hoped someone could specify what snapshot is in
SLES11SP2 and if that snapshot is going to move in the lifetime of
SLES11 (like the kernel did in SP2).[/color]

Suse doesn’t normally comment on what enhancements will or will not be
included in future versions. Very often, when a new version is soon to
be released and they have committed to a specific feature set, they
will discuss some of the features in the upcoming release.

BrainShare is only a few weeks away. I would expect to hear some news
about what’s coming in the next release. If you are able to attend,
that would be a great place to get answers to many of your questions.

If you can’t make it, you can find many of the presentations online
shortly after the conference ends and others who have attended will be
able to share what they have learned.

–
Kevin Boyle - Knowledge Partner
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show your appreciation and click on the star below…

10

horiba wrote:
[color=blue]

Additionally, YAST partitioner lets you activate quotas but then fails
mounting the volume[/color]

I passed on this information and it appears to be a bug. Thank you for
bringing it to our attention.

I was given this link to pass on. It is the only other information
currently available.

https://www.suse.com/products/server/technical-information/#FileSystem

–
Kevin Boyle - Knowledge Partner
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11

A bug was opened:
https://bugzilla.novell.com/show_bug.cgi?id=797499

Quotas should be working in SLES11 SP3.