[DRBD-user] how to drbd the / filesystem device

Joao Ferreira jmcferreira at critical-links.com
Sun May 23 22:29:57 CEST 2010

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


On Mon, 2010-05-03 at 14:02 -0400, Ben Timby wrote:
> Pri/pri would only work if you use a clustered file system such as
> OCFS on your root device. Probably NOT what you are looking for.

correct. I don't want that !... :)

> 
> The difficulty in using DRBD on the root (of course it is possible)

"of course it is possible" ... the magic words :) thx for saying them :)

>  is
> that the initial ramdisk must contain all drivers necessary for
> mounting the root partition. Thus, the initrd must be able to bring up
> the underlying block device, then bring up drbd, pivot to it, and then
> continue the boot process.

Ok. I got this. seems reasonable...

>  The other issue, as already mentioned is
> the secondary machine. It cannot mount the drbd device as it's root
> partition, 

correct. It will have to mount it's own root somewhere else... it will
need to "assume a diferent personality" while in  Secondary mode

> thus failing over to that machine would not be easy
> (possible?) without rebooting.
Yes. possibly...

> Use UnionFS along with another read only root device to provide a
> read/write root device. Both systems are able to boot using just a
> read only device, you then layer in a ramdisk in for writes (log files
> etc) on the secondary machine. Primary machine layers DRBD for writes.
> Replace that ramdisk with the DRBD device when you need to fail over.

thx a lot Ben. you really hit my problem... I'll keep working on it.

thank you everyone !

Joao

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