[DRBD-user] Unable to create Metadata for Tertiary node

Felix Frank ff at mpexnet.de
Mon Feb 4 16:00:59 CET 2013

Note: "permalinks" may not be as permanent as we would like,
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Hi,

On 02/01/2013 06:17 PM, Salman Riaz wrote:
> Hello,
> 
> I am unable to create metadata on tertiary node
> 
> # drbdadm --stacked create-md r0-1
> 
> al_offset 4397912182784
> bm_offset 4397777969152
> 
> Found ext3 filesystem
>   4294836152 kB data area apparently used
>   4294705048 kB left usable by current configuration

wow, is that a 4TB ext3 volume? Impressive.

> Device size would be truncated, which
> would corrupt data and result in
> 'access beyond end of device' errors.
> You need to either
>    * use external meta data (recommended)
>    * shrink that filesystem first
>    * zero out the device (destroy the filesystem)
> Operation refused.

Here is the bad news about stacking: The metadata needs to fit "between"
your data and the lower metadata. In most cases, that means you have to
shrink your filesystem. Note that the remark about external metadata is
in fact not valid for stacked drbd (and should be removed by the
maintainers, hint, hint).

So what you probably need to do is shrink your filesystem by a decent
amount (say, 1GB), then create the metadata for the stacked device, and
then optionally enlarge the filesystem again to use all available space.

Shrinking larger ext3 volumes is quite painful, especially since it
requires a forced fsck beforehand. Make sure to schedule a long downtime.

HTH,
Felix



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