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14.1.1.6 Additional DRBD Configuration Options »
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14.1.1.5. Monitoring and Managing Your DRBD Device

Once the primary and secondary machines are configured and synchronized, you can get the status information about your DRBD device by viewing the output from /proc/drbd: 

root-shell> cat /proc/drbd 
version: 8.0.4 (api:86/proto:86)
SVN Revision: 2947 build by root@drbd-one, 2007-07-30 16:43:05
 0: cs:Connected st:Primary/Secondary ds:UpToDate/UpToDate C r---
    ns:2175704 nr:0 dw:99192 dr:2076641 al:33 bm:128 lo:0 pe:0 ua:0 ap:0
        resync: used:0/31 hits:134841 misses:135 starving:0 dirty:0 changed:135
        act_log: used:0/257 hits:24765 misses:33 starving:0 dirty:0 changed:33

The first line provides the version/revision and build information.

The second line starts the detailed status information for an individual resource. The individual field headings are as follows:

  • cs — connection state

  • st — node state (local/remote)

  • ld — local data consistency

  • ds — data consistency

  • ns — network send

  • nr — network receive

  • dw — disk write

  • dr — disk read

  • pe — pending (waiting for ack)

  • ua — unack'd (still need to send ack)

  • al — access log write count

In the previous example, the information shown indicates that the nodes are connected, the local node is the primary (because it is listed first), and the local and remote data is up to date with each other. The remainder of the information is statistical data about the device, and the data exchanged that kept the information up to date.

For administration, the main command is drbdadm. There are a number of commands supported by this tool the control the connectivity and status of the DRBD devices.

The most common commands are those to set the primary/secondary status of the local device. You can manually set this information for a number of reasons, including when you want to check the physical status of the secondary device (since you cannot mount a DRBD device in primary mode), or when you are temporarily moving the responsibility of keeping the data in check to a different machine (for example, during an upgrade or physical move of the normal primary node). You can set state of all local device to be the primary using this command: 

root-shell> drbdadm primary all

Or switch the local device to be the secondary using: 

root-shell> drbdadm secondary all

To change only a single DRBD resource, specify the resource name instead of all.

You can temporarily disconnect the DRBD nodes: 

root-shell> drbdadm disconnect all

Reconnect them using connect: 

root-shell> drbdadm connect all

For other commands and help with drbdadm see the DRBD documentation.