[DRBD-user] running "the entire machine" off DRBD

Ian! D. Allen idallen at idallen.ca
Thu Sep 23 15:09:39 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 Thu, Sep 23, 2010 at 07:32:56AM -0500, Alex Adriaanse wrote:
> This is a failover setup where all data is replicated to a backup
> server that's located offsite.  I'm not running the entire machine
> from a DRBD disk because that means the root filesystem would have
> to boot from the DRBD device.  Thus, the initrd image would have to
> configure the drbd device, and that's not supported on Debian AFAIK.

You can't run "an entire machine" off DRBD under any conditions, can you?

Since a PC BIOS can't configure and start DRBD, the configuration and
start has to be done by running a kernel loaded by the BIOS from a
non-DRBD partition, which means something outside of DRBD has to boot
up and then get DRBD started, at which point the machine can start using
the DRBD stuff.

Some little piece of the system has to remain outside of DRBD for the
BIOS to boot and to get DRBD started, and that applies to any Linux
distribution, not just Debian.  If you want full back-up of your "entire
machine", that part of the system that is outside DRBD (the part that
actually boots the machine and starts DRBD) has to be copied to the
backup machine by other means.  You can try to make this kernel and its
associated file system as small as possible, but you can't eliminate it.

Am I right?

| Ian! D. Allen  -  idallen at idallen.ca  -  Ottawa, Ontario, Canada
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