DRBD is a block based replication solution, known and available for years under Linux. DRBD allows the implementation of high available systems without SAN. Further use cases are the implementation of storage heads for IP based SANs and long-distance replications over the internet. At present DRBD has a general limitation on two nodes. With DRBD 9 a new release (beta) is under way, allowing for the first time a replication up to 30 nodes. With these features many application possibilities open up for cluster file systems, storage for virtual machines “cloud storage”, and much more.

1. DRBD 9.0: What's New
Philipp Reisner
April, 2013

2. DRBD 8.x in 3 minutes...

3. Feature Spotlight: Connections

4. Connections
• Prior: One resource/device has one peer node
(Available workaround: Stacking)
• Now: Many peers possible
Primary
Secondary
Secondary

5. Connections vs Stacking
• Handling a lot easier
• Activity-Log overhead only once

6. Connections: Full mesh

7. Connections
• Weakly connected • Strongly connected
S
P
S S
P
S

8. Connections
• Strongly connected
S
S
S
• Joining partitions
P P
S S

9. Object model evolution
8.3 – 8.4 – 9.0
drbdadm commandline

10. 8.3 Objects
resource

11. 8.4 Objects
resource
device
1
n

12. 9.0 Objects
resource
device
connection
peer_device
1
n
1
n
1 m
1 m

13. drbdadm arguments
resource
device
connection
peer_device
1
n
1
n
1 m
1 m
drbdadm … res drbdadm … res:conn
drbdadm … res/0:conndrbdadm ... res/0

14. Configuration file changes

15. Configuration: Example
resource example {
volume 0 {...}
volume 1 {...}
on alice { node-id 0; address 10.0.42.1:7000; }
on bob { node-id 1; address 10.0.42.2:7000; }
on clair { node-id 2; address 10.0.42.3:7000; }
connection {
host alice;
host bob;
}
connection {
host alice;
host clair;
}
connection {...}
}

16. Configuration: Example
resource example {
volume 0 {...}
volume 1 {...}
on alice { node-id 0; address 10.0.42.1:7000; }
on bob { node-id 1; address 10.0.42.2:7000; }
on clair { node-id 2; address 10.0.42.3:7000; }
connection-mesh {
hosts alice bob clair;
net {
protocol c;
}
}

17. Configuration
• Disk less nodes
• Connection less nodes

18. Feature Spotlight: Automatic Promote

19. Automatic promote
8.x
drbdadm primary res
mount /dev/drbd0 …
...
umount /dev/drbd0
drbdadm secondary
res
9.0
mount /dev/drbd0
...
umount /dev/drbd0

20. Spotlight: Resynchronisation

21. Resynchronisation
• A node can be sync source to multiple peers
• Happens typically upon initial resync
(--force primary)
Source
Target
Target

22. Resynchronisation
• Sync Target role is serialized among peers
• Usually after temporary node failure
• Paused resync finishes
implicitly
Source
Paused
Source

23. Resynchronisation
• Reconciliation after primary crash
Primary
Secondary
Secondary

24. Resynchronisation
• Reconciliation after primary crash
● The surviving secondaries find out which node is
more recent, and initiate the reconciliation resync
Primary
Secondary
Secondary

25. New Use Cases

26. Use cases: DRBD for access
Primary
Secondary Secondary Storage tierSecondary
Application tier has disk less DRBD devices in primary role
Primary Primary Primary
disk disk disk

27. node 1node 1
Use cases: Scale-out
node 2node 2 node 3node 3 node 4node 4

28. Use cases: Scale-out
• drbdmanage
● Provisioning solution
● Lvm like syntax (lvcreate, lvremove, ...)
● Implemented in python
● Meta data replicated by DRBD

29. The Road ahead

30. The Road ahead
(In no particular order)
• Redundant connections between two nodes
• Support for request-relaying
• Nodes accessing a shared disk
• More than two primary nodes
• Creating of new bitmap-slots online
by changing bitmap-granularity
• UDP multicast transport

31. Hands on!