[DRBD-user] drbd online resize

Stefan Seifert nine at detonation.org
Thu Apr 15 16:26:54 CEST 2010


On Thursday 15 April 2010 16:00:26 Jiri Vitek wrote:

> actualy i have drbd configured as:
> master/slave
> meta-disk: internal
> backd blockevice is sw raid.. /dev/md0
> 
> Now everything is working fine, but due to performance issue i need to
> migrate form sw raid6 level to raid5..
> 
> I have no problem with sw raid online resize. But when resize operation
> will finished, then backing device's size will grow up +250GB
> 
> There is no chance to resize both nodes simultaneously with finish in
> the same time..
> 
> How will drbd handle this situation? when one backing device will be
> bigger then second one.

drbd should handle different disk sizes just fine. Just follow the 
instructuions in the user's guide for online resize. Do _not_ take a node 
offline between RAID resize and drbd resize, as DRBD cannot find it's meta 
data anymore in that case.

You should also really, really consider putting your meta data on a RAID 1. 
You'll only need a couple of megabytes, so even if you used all available 
space on your disks for the RAID 6, there should be some /boot volume which 
you can shrink a little. Putting your meta data on a RAID 1 instead of RAID 5 
or 6 alone should give you a nice performance boost. Maybe you could even 
continue using RAID 6.

Regards,
Stefan SEifert


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