[DRBD-user] Using names instead of IPs in resource 'address' entries

Digimer linux at alteeve.com
Tue Sep 6 19:25:04 CEST 2011

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

On 09/06/2011 01:07 PM, Lars Ellenberg wrote:
> On Tue, Sep 06, 2011 at 12:06:05PM -0400, Digimer wrote:
>> I find myself setting up clusters in one location, then moving them to a
>> second location which requires a new set of IPs. With the other cluster
>> applications, this is not a problem because I can use resolvable names
>> and update just /etc/hosts. However, this doesn't seem to be possible in
>> DRBD.
>> Am I missing something obvious? If it is possible, please let me know.
>> If it's not possible, may I ask why not? Would it be possible to request
>> this ability as a feature request for a future release?
> drbdsetup already does a lookup, and we likely will relax the parser to
> allow hostnames instead of IP addresses as well "soon".
> The basic problem: if the link goes away because of one node chaning its
> IP, we cannot possibly do a dns lookup from kernel space...
> Well, we could. But that would be a good reason to kick us out of the
> kernel and never talk to us again ;)
> So what you would need to do, if you expect the IP to change,
> is to "periodically" run drbdadm adjust, just in case.
> Or ask your cloud provider for persistent addresses...
> If you do not expect the IP to change "at random", just wait a bit, as I
> said this will likely show up as a "convenience" feature" in the near
> future.

Thanks for the explanation.

In my case, this isn't in the cloud. It's much more benal in that I tend
to move clusters between my office and my home lab for various reasons,
and they use different IP space. Really, I should make them compatible,
but that's all secondary to the curiosity of why I couldn't use
hostnames. DNS lookups in kernel space makes sense though. :)

E-Mail:              digimer at alteeve.com
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