[DRBD-user] Re: Manual sync.

Lars Ellenberg Lars.Ellenberg at linbit.com
Mon Oct 17 11:07:45 CEST 2005

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


/ 2005-10-12 18:01:53 -0500
\ Roy Keene:
> All,
> 
> 	I recieved some replies to this, but I think the question has
> 	been misunderstood.
> 
> The backing device on the two machines were once componentns in a DRBD
> array.  One of the machines (machine-2) was turned off and time passed
> (several weeks) so many changes occured on machine-1.  DRBD's sync
> method is VERY slow and mostly stalling on my VPN link, it is
> estimated that it will take atleast 2 months for the 60GB of data to
> sync using DRBD's sync.

which is interessting.  typically drbd sync, if you allow it to, almost
outperforms a plain netcat.

> I can sync it much faster using a method outside of drbd and making
> the backing device on both machines identical.  DRBD doesn't seem to
> be aware of my manual sync and happily tries to continue its own sync.
> My question is:  How can I tell DRBD that my "Inconsistent" component
> is really Consistent ?

anyways:
take DRBD down, so there won't be changes to the data
while your outside-of-drbd-sync is active.
then, netcat the meta-data, too.
if using internal meta data, that already has happened,
and if the underlying block device is of the same size on both nodes,
that should be it. if you use internal meta data, but your underlying
storage is not of the same size, you have to move the meta data into its
expected location on the target device.
if you use external meta data, it is easy: just netcat them, too.

then, if you bring up drbd again, they both see
the same "generation" tags, and if they compare them,
they conclude: "ok, looks like we are equal. no need to sync."

-- 
: Lars Ellenberg                                  Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH            Fax +43-1-8178292-82 :
: Schoenbrunner Str. 244, A-1120 Vienna/Europe   http://www.linbit.com :
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