[DRBD-user] drbd upon md or md upon multiple drbds?

Lars Ellenberg Lars.Ellenberg at linbit.com
Thu Jul 7 23:19:46 CEST 2005

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

/ 2005-07-07 15:51:29 +0200
\ Christof Amelunxen:
> Hi Lars,
> > > From http://www.drbd.org/drbd-article.html
> > > 
> > >         You can stack DRBD on top of md, md on top of DRBD is
> nonsense,
> > >         however.
> > "nonsense"
> > because the drbds would need to be always in Primary on the same
> host...
> > you could do that, meanwhile. but it is not recommended.
> > 
> > if you want real software raid (1,5,10,whatever), then use md,
> > optionally put lvm on top of the md, put drbd on top of md or lvm,
> > and if you really want to, you could then use the drbds as "pv"s in an
> > upper volume group. (the latter is not exactly trivial, either...)
> We have one cluster using drbds as physical volumes and I would just
> like to know what you mean with "not exactly trivial" as for now it
> works like a charm but I dont want to bump into some things I didnt
> think of in advcane later. Are there any special considerations to take
> except that one has to prevent LVM from detecting the underlying
> partitions as physical volumes?

it is "just" remotely possible to encounter funny failure scenarios
where you might not be able to put all drbds into primary state on the
same node for whatever reasons, and thus some pvs for the upper volume
groups are missing...

: Lars Ellenberg                                  Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH            Fax +43-1-8178292-82 :
: Schoenbrunner Str. 244, A-1120 Vienna/Europe   http://www.linbit.com :
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