[DRBD-user] Update: Definitive answer on >4TB DRBD volumes

Lars Ellenberg lars.ellenberg at linbit.com
Thu Jul 24 12:46:22 CEST 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 Thu, Jul 24, 2008 at 10:12:47AM +0100, Lee Christie wrote:
> > > DRBD 8.0.x, 8.2.6:
> > >  32bit kernel:
> > > 	4 TB hard limit per device
> > > 	you can have several of them, but you probably run into some
> > >         other limit pretty fast.
> > >  64bit kernel:
> > > 	4 TB "supported".
> > > 	(unsupported theoretically) 16 TB hard limit per device,
> > 
> > I just tried that myself out of curiosity.
> > it works up to "only" 8 TB per device on 64bit kernel.
> > anything bigger will oops sooner or later.
> > 
> > again: maximum 8 TB per device -- or crash is imminent.
> > 
> > therefore we will restrict drbd-8.2.7 (8.0.13)
> > to refuse anything bigger than that.
> 
> I might be naive here but surely with a 64bit kernel it should be
> possible to go over 8TB and if you cannot then there must be a bug
> somewhere ?

no, not a bug. but a
"shortcoming of the current implementation."

as I said:

> we plan to increase the limit on DRBD+ up to 128 TB (or even                                                                      
> "arbitrary") per device "soonish".                                                                                                
> once that is done, the current DRBD+ code will be migrated,                                                                       
> which would make 16 TB per device supported in 64bit "plain"                                                                      
> DRBD 8.2.y, where y is several steps larger than 6.                                                                               
                                                                                                                                    
this remains true, however.

-- 
: Lars Ellenberg                           http://www.linbit.com :
: DRBD/HA support and consulting             sales at linbit.com :
: LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
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