[DRBD-user] drbd 0.8 active/active and lvm - What stupid thing am I doing?

Graham Wood drbd at dragonhold.org
Wed Jan 17 01:17:28 CET 2007

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


I've got a problem with trying to setup a cluster arrangement (using clvmd, from redhat 
cluster) using v0.8rc1 on debian etch.  I'm hoping this is down to me being stupid - since 
it'd be such a nice setup if it worked *grin*

Basically it doesn't seem that writes to node1 are copied to node2 properly, but writes to 
node2 /are/ copied to node1.

Both machines are K7 CPUs with 1GB memory, and a pair of 80GB IDE disks mirrored.  /dev/md4 
is then mirrored between the nodes using drbd to produce /dev/drbd0.

drbd runs over a separate VLAN to most other traffic - over bond1 (which is a pair of 8169 
gigabit cards) - and the redhat cluster suite uses this as a secondary link (bond0 is the 
primary link for the cluster as well as the public interface, since it's a very limited vlan 
anyway). 

I don't think the HW is relevant (I ran memtest86+ and badblocks on both systems for 24 
hours each before this, so I'm happy the HW is OK) - but it's included in case that's where 
I'm being stoopid.

I've done various steps, and run md5 on the drbd device / lv on top of it at each step:

	dd if=/dev/zero of=/dev/drbd0 bs=1M count=100 on Node1
		Node1: 2f282b84e7e608d5852449ed940bfc51  -
		Node2: 2f282b84e7e608d5852449ed940bfc51  -

	dd if=/dev/random of=/dev/drbd0 bs=1M count=100 on Node1
		Node1: b096e3d5bc24215d56207d1d6b9ea1d6  -
		Node2: b096e3d5bc24215d56207d1d6b9ea1d6  -

	pvcreate & vgcreate on Node1
		Node1: 7229ff35a7beb80cf9aca91a01cfadfa  -
		Node2: 7229ff35a7beb80cf9aca91a01cfadfa  -

	lvcreate /dev/shared/mysql 1G lv
		Node1: f935fef26a51ea329892571a4a7e0922  -
		Node2: f935fef26a51ea329892571a4a7e0922  -

	dd if=/dev/zero of=/dev/shared/mysql on node1 (md5 now of partition, not raw device)
		Node1: cd573cfaace07e7949bc0c46028904ff  /dev/shared/mysql
		Node2: cd573cfaace07e7949bc0c46028904ff  /dev/shared/mysql

	mkfs.ext3 on node1
		Node1: 8ce6e30b21fb273e4486926d259a79df  /dev/shared/mysql
		Node2: 8ce6e30b21fb273e4486926d259a79df  /dev/shared/mysql

	mount, restore tar file, unmount
		Node1: ccf7174e9d67c5974a42de2b0c0771ad  /dev/shared/mysql
		Node2: c15ccb3f19563250bffc772e75c489aa  /dev/shared/mysql

	dd device to local file on each node, and md5sum that.
		Node1: ccf7174e9d67c5974a42de2b0c0771ad  /mysql.dump.Node1
		Node2: c15ccb3f19563250bffc772e75c489aa  /mysql.dump.Node2

	dd file on node1 back to lv volume
		Node1: ccf7174e9d67c5974a42de2b0c0771ad  /dev/shared/mysql
		Node2: bb7a5b87411bfbee2187d23039500a6a  /dev/shared/mysql

	dd file on node2 back to lv volume
		Node1: c15ccb3f19563250bffc772e75c489aa  /dev/shared/mysql
		Node2: c15ccb3f19563250bffc772e75c489aa  /dev/shared/mysql

	dd file on node1 back to lv volume
		Node1: ccf7174e9d67c5974a42de2b0c0771ad  /dev/shared/mysql
		Node2: ba4a3f2fc6cddff2595ac201d6696558  /dev/shared/mysql

	do the same thing again
		Node1: ccf7174e9d67c5974a42de2b0c0771ad  /dev/shared/mysql
		Node2: 98232fef6be35d23d2af54c2ea037836  /dev/shared/mysql
	
	now using dd from Node2 to restore the dump file from node1 (scp'd across)
		Node1: ccf7174e9d67c5974a42de2b0c0771ad  /dev/shared/mysql
		Node2: ccf7174e9d67c5974a42de2b0c0771ad  /dev/shared/mysql

	dd zero it from node2
		Node1: cd573cfaace07e7949bc0c46028904ff  /dev/shared/mysql
		Node2: cd573cfaace07e7949bc0c46028904ff  /dev/shared/mysql


So can anyone tell me what blindingly obvious thing I've missed - please??? :)

Graham




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