[DRBD-user] DRBD 84 resyncer runs out of memory

Lars Ellenberg lars.ellenberg at linbit.com
Mon Feb 15 15:29:39 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.


On Fri, Feb 12, 2016 at 04:10:14PM +0000, freebird wrote:
> Hi, I have a memory usage problem with the resync sender on a single
> resource.  If the total size of the out of sync blocks exceeds the
> memory size when drbd connects, the sync progresses until it exhausts
> the memory leading to the OOM killer kicking in (too slowly to make
> any difference) followed by a kernel panic.  Everything else including
> replication of very large files that exceed the memory size, works
> fine.
> 
> I've tested with out of sync sizes up to just short of the total
> memory when the resync succeeds and observed that the memory used
> increases in line with sync'ed blocks i.e. the resync process seems to
> be allocating memory per block and doesn't release or reuse it ...
> only when the resync completes does the memory get released.  The
> strange thing is that I can't find which specific process is retaining
> the memory ... nothing shows up in top, slabtop or the process table.

We regularly resync terrabytes of dummy data in test VMs that have
only a few hundred megs of ram allocated. So I seriously doubt
that this was a generic DRBD issue, but would suggest that
something is off in your deployment.

-- 
: Lars Ellenberg
: http://www.LINBIT.com | Your Way to High Availability
: DRBD, Linux-HA  and  Pacemaker support and consulting

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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