[DRBD-user] DRBD9 (9.0.1) - some testing results

Eugene Istomin E.Istomin at edss.ee
Wed Feb 17 17:34:27 CET 2016

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


we done some tests with DRBD9 9.0.1

Some preliminary results:

####  1. Verify depends on "connection-mesh" position. ####

      connection-mesh {
          hosts 6787-dblapro-edss 6788-dblapro-edss 6789-dblapro-edss;

If the first node is switched off - verify on the second if failed:
6788-dblapro-edss# drbdadm verify all
storage: State change failed: (-15) Need a connection to start verify or resync
Command 'drbdsetup verify storage 0 0' terminated with exit code 11

storage role:Secondary
  6787-dblapro-edss connection:Connecting
  6789-dblapro-edss role:Secondary

After "drbdadm up all" on the first (6787-dblapro-edss) and "drbdadm down all" on the second (6788-dblapro-edss) seems working correctly (with node 2 unavailability problems, but thats ok)

storage role:Secondary
  6787-dblapro-edss role:Secondary
    replication:VerifyS peer-disk:UpToDate done:100.00
  6788-dblapro-edss connection:Connecting

So, "connection-mesh" host position matters (not just for verify, may be).

####  2. Verify strange verify behaviour ####

the same three nodes, start with fully OK status for all nodes.

#storage role:Primary
  6788-dblapro-edss role:Secondary
  6789-dblapro-edss role:Secondary

Than, the magic:
     1. On first (Primary role) node# mount /dev/drbd/by-res/storage/0 /media/storage# dd if=/dev/urandom of=/media/storage/1 bs=1M count=100-rw-r--r-- 1 root root 104857600 Feb 17 18:17 /media/storage/1

     2. Down Second node and mount as ordinary disk (we use external metadata)

     3. Second node - verifywait till sync is done

		# ... storage role:Secondary
	  6787-dblapro-edss role:Primary
   	 replication:VerifyS peer-disk:UpToDate done:100.00
	  6789-dblapro-edss role:Secondary
   	 replication:VerifyS peer-disk:UpToDate done:100.00

     1. Mount Secondary node disk (assuming to see only "./1" file)# drbdadm down all# mount /dev/disk/by-label/storage /media/storage/# ls -l /media/storage/
		-rw-r--r-- 1 root root 104857600 Feb 17 18:21 1
		-rw-r--r-- 1 root root 104857600 Feb 17 18:21 2

What really verify do? 

#### 3. No information about speeds, timing & bandwith ####

How long will replication lasts?
What is current bandwidth?
The questions are for initial sync. resync & verify.

BTW, current implementation (for ex. done:80.94) is faulty sometimes.

Thanks for DRBD9 mesh topology! =)
/*Best regards,*/
/Eugene Istomin/

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