[DRBD-user] moving to a different backing device

Wayne lists-drbd at useunix.net
Thu Feb 20 02:34:48 CET 2014

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

I currently have DRBD 8.3 working between 2 Debian boxes with external
RAID storage as the backing device. I intend to update the RAID storage
on each system since they are rather old now. I need to do this with
minimal down time of course. What is down-time ever maximal, LOL?

The backing stores on each system right now are identically sized
logical block devices (LUNS) exposed by the RAID hardware.

I've already installed one RAID onto the secondary DRBD system. My plan
is to take the secondary DRBD offline, use 'dd' to move the data from
the current RAID to the new RAID, reconfigure the backing device to the
new RAID and set DRBD online. I'm hoping this will only require a
re-sync of the blocks that have change since the secondary was brought

I believe a problem is that the new backing device is much larger than
the current backing device. So a straight dd won't place the meta-data in
the correct position on the new block device? Is this a correct
assumption? If so what is the correct way to handle this migration while
minimizing re-sync time?

Is this even the correct approach? This is my first crack at this so I
may be way off.

Any and all help is appreciated.


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