[DRBD-user] Estimating meta data size

Lars Ellenberg lars.ellenberg at linbit.com
Tue Dec 2 15:49:35 CET 2008

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


On Tue, Dec 02, 2008 at 10:38:46AM +0100, Stefan Seifert wrote:
> On Tuesday, 02. December 2008, Lars Ellenberg wrote:
> > On Tue, Dec 02, 2008 at 09:58:18AM +0100, Stefan Seifert wrote:
> > > On Tuesday, 02. December 2008, Florian Haas wrote:
> > > > Presume you're packing metadata for several resources into one metadata
> > > > device using "meta-disk <device>[<index>]". When you do that, each
> > > > metadata area is fixed at 128M. With eight resources, you'll fill up
> > > > your 1G metadata device.
> > >
> > > And please note that 8.27 is more strict on this than 8.2.6! This bit me,
> > > because my meta data device for two drbd devices was a few MB short and
> > > after what was supposed to be a small upgrade, drbd wouldn't start
> > > anymore.
> >
> > interessting. you should have complained ;)
> > maybe we can relax that a bit again...
> 
> Well it was clearly my fault. The docs say 128MB for each drbd device and I 
> gave it about 249 for two (maybe fdisk rounded down when partitioning).
> 
> What I wonder is, why the difference between internal and external meta data? 
> If it only needs 5MB, why require 128?

hysterical reasons.

you can also use _flexible-external_, which is not index-able.
but it will be satisfied with only one MB,
if that is enough to support your data area.  actually, I think it will
clip your ll dev to the amount of bitmap the meta devive can support.

-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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