[DRBD-user] DRBD over RAID1 / Pacemaker failure detection

Caspar Smit c.smit at truebit.nl
Tue Jun 1 15:17:52 CEST 2010

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Hi all,

I've been using DRBD/Heartbeat for a while now in heartbeat v1
(haresources) style configuration.

I'm now moving to heartbeat v3/pacemaker because i like the resource level
failure detection.

I've created a working setup:

- 2-node cluster
- MDADM RAID1 of two disks (sdb and sdc) on both nodes (md0)
- DRBD on top of the RAID1's (drbd0)
- iscsitarget (IET) exporting /dev/drbd0
- failover IP
- node 1 is preferred master.
- Using the Linbit OCF RA script that comes with v8.3.7.

I tested the following situation:

- I pulled out BOTH sdb and sdc on node 1.
- Did a write action on the iscsitarget from a client machine.
- DRBD (on-io-error detach) detached the primary node 1 and became:
  Primary/Secondary - Diskless/UpToDate
- The performance degraded significantly after it became diskless.

Is it possible for the Linbit OCF RA script to detect that a low level IO
error occured on the DRBD backed storage (md0)?

What I would like is that in a case of low level failure (software raid
failure) that a failover takes place and node 2 becomes the primary
because now that doesn't happen.

Kind regards,
Caspar Smit

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