On Mon, May 10, 2010 at 03:09:57PM +0200, Katharina Haselhorst wrote:
> Hello,
>
> I've a question concerning the truck based replication. Following
> scenario: Host A is working with a device in primary role in
> standalone mode. It is continuously writing data to the device. Host
> B does not have any of the data and should be synchronized as far as
> possible to the device of host A.
>
> According to the instructions on the drbd website, I do drbdadm --
> --clear-bitmap new-current-uuid resource, archive the device images
> (including the metadata), send them to B and do a drbdadm
> new-current-uuid resource.
>
> My question: Is it possible for Host A to keep writing between the
> first command (with --clear-bitmap) and the archivation of the
> device image?
Yes.
Starting with old uuid, possibly partially dirty bitmap.
[A] Generate new uuid, clean bitmap.
The now clean bitmap will be re-dirtied with
everything that is written from now on.
[B] Disk gets pulled, imaged, whatever.
[C] Second new uuid generated.
(*NOT* clearing the bitmap this time)
This marks the end of the imaging/disk pulling.
Bitmap contains everything that has been redirtied since [A]
[D] bitmap continues to be updated.
[E] Connect of image (from [B]) to current:
normal bitmap based resync.
Everything that has been re-dirtied since [A] will be resynced.
> Or do I have to suspend Host A (at least the
> application writing to that device) for that time?
No.
If you can minimize write activity between [A] and [E],
you will have a minimal resync.
--
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com
DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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