[DRBD-user] Sync stuck at 100%

[Per Liden]

On Thu, 25 Nov 2004, Per Liden wrote:

[...]
> I'm having problems with DRBD getting stuck at around 99-100% during an 
> initial/full sync. This seems to be happening about 8 out of 10 times.

After some further testing it seems that I managed to resolve the issue.

Changes I made to my configuration:
- Removed LVM (DRBD now runs directly on top of my hda10 device).
- Changed meta-data to "internal" (instead of hda9 [0]).
- Filesystem used on top of /dev/drbd0 is now reiserfs instead of ext3.
  (I thought I should mention is, even if the choice of filesystem 
  shouldn't have anything to do with my sync problem).

So far I've done three full syncs without getting stuck. Unfortunately I 
did all the above changes in one go, so I can't really say if it was LVM 
or the separate meta-data partition that casued the problem. My guess is 
LVM though.

Whether I can live without LVM is something I'll have to look into...

[...]
> Interesting to note is that the nodes seem to have different ideas about 
> how much data needs to be synchronized, i.e.:
>   Nov 25 11:07:03 Proc1 kernel: drbd0: Resync started as SyncSource (need to sync 60812372 KB [15203093 bits set]).
> vs.
>   Nov 25 11:07:04 Proc2 kernel: drbd0: Resync started as SyncTarget (need to sync 60558500 KB [15139625 bits set]).

After my reconfiguration I haven't seen any thing like this again. Every 
time a sync is initiated both nodes have a common understanding of the 
number of bytes that need to be synchronized.

I also noticed that the average sync rate was much higher and more stable 
after my changes. Before the sync fluctuate between 1,000 and 25,000 Kb/s 
with an average of ~10,000 Kb/s. With my changes the sync rate was fairly 
stable with an average of ~20,000 Kb/s (sync rate was set to 30M in both 
configuration).

/Per