These are the slides of our SUSECon 2013 presentation with Arvin (the inventor of Snapper) Btrfs as technology has been getting a lot of attention over the past few years. While interesting for its feature set alone, like checksums, copy on write, snapshots and built-in device management, without proper management tooling and integration with other parts of the operating system, it is difficult for the average user to use Btrfs to its full potential. This session will help you understand the features of Btrfs and how Snapper can be used for snapshot management in SUSE Linux Enterprise. We also will provide use cases and an outlook for future functionality.

1. Btrfs and Snapper
The Next Steps From Pure Filesystem
Features to Management Integration and Compliance
SUSECon 2013, Orlando, Florida
Gábor Nyers
Arvin Schnell
Sr. System Engineer @SUSE
gnyers@suse.com
Sr. Software Developer
aschnell@suse.com

2. Abstract
Btrfs as technology has been getting a lot of attention over
the past few years. While interesting for its feature set alone,
like checksums, copy on write, snapshots and built-in device
management, without proper management tooling and
integration with other parts of the operating system, it is
difficult for the average user to use Btrfs to its full potential.
This session will help you understand the features of Btrfs
and how Snapper can be used for snapshot management in
SUSE Linux Enterprise. We also will provide an outlook for
future functionality.
2

3. Agenda
Btrfs in SUSE distro's
Snapper
Btrfs Use cases
Summary and
Questions
3
•
Btrfs specs
•
Introduction to Btrfs
Features and Concepts
•
Current limitations
•
Support from distributions
•
Demo1: Convert and Resize

4. Prelude: Growth of storage
Can traditional filesystems keep up with this growth?
4

5. What People Say About Btrfs...
Chris Mason (lead developer Btrfs)
‒
General purpose filesystem that scales to very large storage
‒
Focused on features that no other Linux filesystems have
‒
Easy administration and fault tolerant operation
Ted Tso (lead developer Ext4)
‒
(Btrfs is) “... the way forward”
Others:
‒
‒
5
“Next generation Linux filesystem”
“Btrfs is the Linux answer to ZFS”

6. Why Another Linux filesystem?
•
Solve Storage Challenges
‒
‒
Dynamic Resources (expand and shrink)
‒
Storage Management
‒
6
Data Integrity
‒
•
Scalability
Server, Cloud – Desktop, Mobile
Compete with and exceed the filesystem capabilities
of other Operating Systems

7. Btrfs Specs
•
Max volume size
: 16 EB (2^64 byte)
•
Max file size
: 16 EB
•
Max file name size
: 255 bytes
•
Characters in file name : any, except 0x00
•
Directory lookup algorithm : B-Tree
•
Filesystem check
•
Compatibility
‒
7
: on- and off-line
POSIX file owner/permission
Access Control Lists (ACLs)
Asynchronous and Direct I/O
Hard- and symbolic links,
Extended Attributes (xattrs),
Sparse files

8. Btrfs Feature Summary 1/2
•
Copy-on-write
‒
•
Never overwrite data!
Multi-device
Management
‒
•
‒
‒
8
At file system level
RO / RW
on-line add and remove of
devices
Light weight
‒
•
‒
Snapshots
mixed size and speed
In-place conversion from
Ext[234] to Btrfs
•
Object level RAID:
‒
•
0, 1, 10
SSD support
(optimizations, trim)

9. Btrfs Feature Summary 2/2
•
Checksums on data and
meta data
Send/Receive
Grow and shrink(!)
‒
Scrub
‒
‒
Defragmentation
Similar to ZFS' send/receive
function
Balancing
‒
9
Quota groups
On-line filesystem
management:
‒
•
•
•
•
Transparent
compression (gzip, lzo)
•
Seed devices
‒
•
Overlay a RW file system
on top of an RO
Data de-duplication:
‒
Background de-dup
process (see also bedup)

10. Supported Btrfs features in SLES 11 SP3
Supported
Unsupported
‒
‒
Auto Defrag
‒
Copy-on-Write
‒
Btrfs Built-in RAID
‒
Subvolumes
‒
Compression
‒
Metadata Integrity
‒
Send / Receive
‒
Data Integrity
‒
Hot add / remove disks
‒
Online scrubbing
‒
Seeding devices
‒
Manual defrag
‒
10
Snapshots
Multiple devices
(using MD or LVM)

11. Btrfs Planned Features
•
Object-level RAID 5, 6
•
Data de-duplication:
‒
•
On-line de-dup during
writes
Tiered storage
‒
‒
11
Frequently used “hot” data
on SDD(s)
“Archive” on HDD(s)
ToDo
:

12. Demo: Btrfs Convert and Resize
•
Convert existing Ext3 to Btrfs
•
On-line re-size of Btrfs
‒
‒
12
Grow
Shrink

13. Btrfs Concepts
•
•
Subvolume
•
13
Extents and Chunks
B-Tree
•
Snapshot

14. Btrfs Concepts:
Extents and Storage Organization
Chunks
Metadata
M
M
Raw data
D
D
Default sizes
D
4 Kbyte
512 byte
Blocks
Block layer
Extents
1 GB
sda
md0
HW
sdc
14
sdd
sdb
# btrfs filesystem df /
Data: total=14.50GB, used=12.20GB
System, DUP: total=8.00MB, used=12.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.75GB,
used=904.11MB
# df -h /
Filesystem
Mounted on
/dev/sda7
#
Size
Used Avail Use%
20G
Disk utilization
12,2GB + 2x 0,9GB + = 14 GB
14G
4.3G
77% /

15. Btrfs Concepts:
Subvolumes
Default
Subvolume
Root node
Subvolume(s)...:
/
… appear to be a directory
/home
… start as an independent but
empty root node
/var/log
… are independently mountable
Subvolume
Root node
Subvol
(B-Tree)
15
Subvolume
Root node
Subvol
(B-Tree)
… are independently
snapshotable
… are “equals” amongst each
other, but there is a designated
“default subvolume”

16. Btrfs Concepts:
Snapshots
Snapshot(s)...:
/
… are an independent clone of
the state of a subvolume
/home
Clone
B-Tree
Subvol
(B-Tree)
… share all raw data with its
ancestor after creation
Clone
B-Tree
… may be (practically) unlimited
in number
… are either RO or RW
… may be “nested”, that is
“snapshot of a snapshot”
16

17. Btrfs Features:
Current(*) limitations – real or perceived
•
Full featured off-line fsck
tool, however:
‒
Implementation of
off-line fsck already
available
‒
On-line repair options with
btrfs scrub
‒
extended repair function
with 'recovery' mount option
‒
`btrfs restore` tool
(*) as of Oct 2013
17
•
Limited bootloader
support (GRUB2 only)
•
RAID 5 and 6
(patch available)
•
Quality of technical
documentation could be
better

18. Btrfs Support Status – Distros
Support
•
SUSE Linux Enterprise
Server 11 SP2+
Technology Preview /
unsupported
®
•
Red Hat Enterprise Linux
•
•
Fedora
•
Oracle Linux 6 with
UEK2+
•
and others...
•
Debian 6+
•
18
OpenSUSE 11.4+
Ubuntu 11.04+

19. Agenda
Introduction to Btrfs
•
Btrfs integration in SLES and
openSUSE
Btrfs in SUSE distro's
Snapper
•
Partitioner
•
Planned features
•
Filesystem recommendations
•
Demos
Btrfs Use cases
Summary and
Questions
19

20. Btrfs integration in
SLE 11 SP3 and openSUSE 12.3 – 13.1
•
Installer
•
Snapper
‒
‒
Manage snapshots
‒
Recommendation for
subvolume layout
‒
Automatically create
snapshots
‒
•
Btrfs as root file system
Btrfs support in AutoYaST
‒
Display differences between
snapshots
‒
Roll-back
Partitioner
‒
‒
20
Create Btrfs
Create subvolumes

21. Btrfs integration in YaST Partitioner
21

22. A Few Recommendations 1/3
Purpose driven filesystem choices, ie: what
filesystems to choose for what use case?
Please see session TT1376
Matthias Eckermann (SUSE Product Management)
Jeff Mahoney (SUSE Kernel Team)
22

23. A Few Recommendations 2/3
Free disk space:
‒
Starting: ~30% filling
‒
Subvolumes layout
‒
Directories containing logs
to avoid log roll-back
Operation: <90% filling
‒
Directories w/ high volume
write I/O, like:
/tmp, /srv,
/var/spool,
/var/log, /var/run,
/var/tmp, /opt:
should be on their own
subvolumes, or a non-Btrfs
filesystem;
Especially on rotating
disks!
23

24. A Few Recommendations 3/3
A proposed filesystem maintenance plan
•
Preparations
‒
•
•
Get a baseline on “Hot
zones” for a period of
ca. 1 week – 1 month
‒
‒
Monitor free space
Monitor performance impact
of “Hot zones”
•
if Btrfs on / Manual defrag
(if Btrfs on HDD, instead of
on SSD)
‒
Daily maintenance
‒
Weekly maintenance
Check / remove unneeded
snapshots
Monthly maintenance
`btrfs file balance`
‒
24
re-evaluate need for
filesystem extension
‒
‒
‒
re-evaluate subvolume
layout
Scheduled Scrub

25. Demo: Dealing with fragmentation
Specifically for HDDs, file fragmentation caused by the CoW feature may
impact disk I/O performance. To prevent performance degradation,
regular de-fragmentation is advisable.
•
Find the top 10 most
fragmented files in the
current directory:
filefrag * | sort -nr -k 2
head -10
•
files:
btrfs file defrag $file
‒
directories:
btrfs file defrag /var/log/
‒
whole filesystem:
btrfs file defrag /
25
Hot zones:
‒
system specific:
/var/log/journal/
/tmp
‒
user specific:
/home/
|
Defrag
‒
•

26. Btrfs integration in SLE 11 and openSUSE
Future plans
•
YaST partitioner support
for:
‒
Built-in multi-device
handling and RAID
‒
Transparent compression
•
•
26
Bootloader support for
/boot on btrfs (SLE12)
Snapshot integration into
bootloader

27. Btrfs References
Publications
•
Btrfs wiki (and mirror)
•
Josef Bacik's article on Btrfs
•
Arne Jansen's paper on
qgroups (quota support)
Video's
•
•
•
Oloh Rodeh - B-trees,
Shadowing, and Clones, IBM
Research paper
LWN - “A short history of btrfs”
article
•
Matthias Eckerman: Why btrfs is the
Bread and Butter of Filesystems,
LinuxCon 2013, New Orleans
(49min, link)
•
Chris Mason: Introduction to Btrfs
(26min, link)
•
Chris Mason: Btrfs Filesystem: Status
and New Features, (May 2012, link)
•
Avi Miller's Btrfs talk at LinuxConf AU
(49min, Jan 2012)
‒
‒
Wikipedia - Btrfs article
•
Demo of “mount -o recovery”
Animations of disk usage on Ext3,
XFS and Btrfs
Douglas Fuller's talk
(24min, Apr 2011)
‒
27
Nice performance demo's

28. Snapper: snapshot management
Functions
•
Create / Delete
snapshots
‒
Also for non-root users
through DBus
Compare snapshots
‒
List of files
‒
28
•
Undo changes, ie: per
file rollback
•
Mount / Unmount
snapshots
Automated
‒
•
Store and manage
additional snapshot
related metadata
Manually
‒
•
Content of files (diff)

29. Snapshot management with Snapper
29

30. Snapper DBus support
Unprivileged
user
Unprivileged
user
Privileged user
•
Snapper is split up:
‒
‒
agent
(snapper)
agent
(yast)
agent
(e.g.: custom
script)
snapper (client)
snapperd (server)
•
Authorized users submit
request through DBus
•
snapperd performs
actions on behalf of users
•
Authorization scheme
dbus daemon
snapperd
Privileged user
30
‒
Users
‒
Agents

31. Snapper configuration
•
YaST configures snapper
for the root filesystem
•
Cleanup Algorithms:
NUMBER_LIMIT="10"
‒
•
‒
TIMELINE_LIMIT_DAILY="
5"
/etc/snapper/configs/
contains a file for each
btrfs subvolume:
•
Permissions:
‒
‒
ALLOW_USERS="tux"
‒
31
cleanup algorithms
snapshot creating
permissions
‒
chgrp users /home/tux

32. Snapper – Metadata
Meta information stored with each snapshot:
‒
: [ Pre | Post | Single ]
‒
#
: Nr of snapshot
‒
Pre #
: Matching “Pre” number, if type is “Post”
‒
Date
: Timestamp
‒
User
: User who created the snapshot
‒
Cleanup
: Cleanup algorithm for this snapshot
‒
Description : A fitting description of the snapshot (free text)
‒
32
Type
Userdata
: key=value pairs to record all sorts of useful
information about the snapshot in an
(e.g.: easily parsing from scripts)

33. Distro Support Status - Snapper
Support
•
SLES 11 SP2
Technology Preview /
unsupported
SLES 11 SP3
•
Red Hat Enterprise Linux
•
openSUSE 12.1 - 13.1
•
Fedora
•
Fedora 19
•
and others...
•
33

34. Snapper – Planned features
•
Keep track of space usage
by snapshots, utilizing
qgroups;
In other words: how much space will
be reclaimed when deleting a
snapshot
•
Integration points
‒
Hooks for external scripts
‒
‒
34
Snapshot create
Snapshot delete

35. Demo
Snapper
•
•
Snapper integration with YaST
•
Snapper command line tool
•
35
Snapper module for YaST
Snapper as non-root

36. Agenda
Introduction to Btrfs
•
Filesystem changes after
software installation
Btrfs in SUSE distro's
Snapper
•
Server side copy with
Samba4
•
Automated Recovery Points
with Samba4
•
ITIL Change Management vs.
DC reality
Btrfs Use cases
Summary and
Questions
36

37. Use Case: Filesystem changes after
installation of some software
•
Step 1: Create “Pre”
snapshot
snapper create --type pre
--description "Before
installation”
•
Step 2: Install application
•
Step 3: Create “Post”
snapshot
snapper create --type post
--pre-number $PreNR
--description “After
installation”
37
•
Step 4: Compare “Pre” and
“Post” situation
# snapper status $PreNR..$PostNr
c... /etc/ld.so.cache
+... /usr/lib/libXi.so.6
+... /usr/lib/libXi.so.6.1.0
c... /var/cache/ldconfig/aux-cache
[...]

38. Use Case:
Server Side copy with Samba4
•
Prolem:
‒
•
Solution:
‒
•
Copying of large file(s)
initiated from workstation is
slow and requires large
bandwith
Clone file(s) on the server
Required:
‒
‒
38
Samba 4.1
(supports Server side copy)
Client: Windows Server
2012

39. Use Case:
Automated Recovery Points with Samba4
Scheduled snapshots by Snapper
Available Recovery Points for “test.txt” in Explorer
Samba4
service
File
share
SLES 12
Network
share
Windows 7,
Vista or XP
39
Automated
snapshots
File “test.txt” is changed
File “test.txt” is created
Now

40. Use Case:
ITIL Change Management vs. DC reality
•
ITIL Change
Management
‒
‒
•
What is the status of
planned changes?
Are there any unplanned
changes?
•
DC reality
‒
Unplanned, unauthorized
and ill-considered changes
do happen
Solution option
‒
‒
Snapper integration with systems management tooling to track
changes
‒
Record Change related information in snapshot metadata
‒
40
Use Btrfs snapshots to preserve states of systems
Automated interface from Snapper to ITIL tooling

41. Use Case:
ITIL Change Management vs. DC reality
# @Begin of implementation Change:
snapper create
--type pre
--description "ChgMgt Work order: Upgrade syslog configuration
to forward log entries to central log server"
--userdata
"WorkOrder=201201253030000012-1,
State=InProgress,Agent=jdoe@example.com"
# @End of implementation Change:
snapper create
--type post --pre-number 240
--description "Done: ChgMgt Work order: Upgrade syslog
configuration to forward log entries to central log server"
--userdata "WorkOrder=201201253030000012-1, State=Closed,
Agent=jdoe@example.com"
41

42. Agenda
Introduction to Btrfs
Summary
•
•
Development is ongoing
•
Distributions support is mounting
•
Lots of practical applications yet to
come
•
Btrfs in SUSE distro's
Snapper
Lots of desirable features
Please direct your questions or
remarks to
Gábor Nyers <gnyers@suse.com>
Btrfs Use cases
Summary and
Questions
42

43. For more information please
visit our website:
www.suse.com
Thank you.
43

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