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

Lars Ellenberg lars.ellenberg at linbit.com
Thu Jul 24 12:50:13 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 05:43:28PM +0800, Patrick Coleman wrote:
> On Thu, Jul 24, 2008 at 4:34 PM, Lars Ellenberg
> <lars.ellenberg at linbit.com> wrote:
> > On Tue, Jul 22, 2008 at 12:01:48PM +0200, Lars Ellenberg wrote:
> >> On Tue, Jul 22, 2008 at 05:03:23PM +0800, Patrick Coleman wrote:
> >> > Hi,
> >> >
> >> > I've googled around for a while, and I can't find anything definitive
> >> > for or against - what is the maximum volume size supported by DRBD?
> >> >
> >> > I'm running an 11TB DRBD 8.2.6 volume between two nodes, connected by
> >> > 10GE. I've hit some odd issues (OOPSes, continually resyncing data)
> >> > and I'd like to eliminate the volume size as a cause of the issue.
> >>
> >>
> >> 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.
> 
> Cool. Just to clarify - the 8TB limit is global or per resource?

yes.
 :)

I think I was pretty clear in that post.
where I wrote "per device" I meant "per device".
where I wrote
>       you can have several of them, but you probably run into some                                                                
>       other limit pretty fast.                                                     
I meant exactly that.

> That is, can I safely have two 6TB devices (assuming I have sufficient
> memory to handle the bitmaps)?

you can try. it might work.

-- 
: Lars Ellenberg                           http://www.linbit.com :
: DRBD/HA support and consulting             sales at linbit.com :
: LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
: Vivenotgasse 48, A-1120 Vienna/Europe     Fax +43-1-8178292-82 :
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