[DRBD-user] LVM as backing store on 3rd node - snapshot problem

Miles Lott mlott at gie.com
Thu Sep 13 16:36:22 CEST 2012

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

We are currently running version 8.4.2 on Centos 6.3 in a test 
environment which is nearing production status.  Last week we finally 
setup our 3rd node which will ultimately be located offsite.  Currently, 
it is still in-house on a 1Gb/S ethernet connection.

All 3 nodes are using LVM as the backing store.  For the 3rd node, our 
intention was to create and maintain a single, nightly LVM snapshot.  We 
are currently in the process of rsyncing data from the old server to the 
new DRBD setup.  The snapshot is causing problems.

During the time that the rsync is active (data is changing in the 
filesystem on DRBD) and the lvm snapshot exists on the 3rd node, the 3rd 
node is regularly timing out.  This causes a resync from the primary 
node, which also times out, disconnects and reconnects and so on.  I 
have seen the speed dip to near 0k/S before the timeout.

As soon as I removed the nightly snapshot from the 3rd node, the speed 
of the resync crept back up to normal.  As the rsync process continues, 
the connection is no longer timing out.

So, is this normal, obvious, or a bug?  In any case I'll need to find a 

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