[DRBD-user] 4TB limit

Lars Ellenberg lars.ellenberg at linbit.com
Wed May 25 16:27:31 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 Wed, May 25, 2011 at 02:11:08PM +0200, Lionel Sausin wrote:
> That's interresting. We use internal md indeed.
> Lionel.
> 
> Le 25/05/2011 14:04, Mikael Andersson a écrit :
> > I do still have issues getting /dev/drbd1 device to come over 4TB limit (4293787648 byte)
> > Now I think I have tested just about everything I can come up with, I found something I don't understand.
> >
> > When I configure "meta-disk internal" then I get what I want in size, about 9TB.
> > But when I set "meta-disk /dev/sdb1[1]" I get the 4T limit.

Works as designed.

Maybe needs an additional sentence in bold in the man pages
and User's Guide.

indexed external meta data is limited to 128 MiB:
meta-disk  /dev/sde[3]; e.g. would live in megabytes 384 to 512 of sde.
So it only has room for just below 4 TiB.

_flexible_ meta data is allowed to use up all available space of the meta data device.
internal meta data is always flexible (with DRBD versions >= 8.x).
iirc, that would look like
flexible-meta-disk /dev/sde;

> > Then I tested 1GB as md size, thinking more than enough, no difference.
> > I also calculated the size using http://www.drbd.org/users-guide/ch-internals.html#s-external-meta-data , but with no luck.
> > I made sure I didn't calculated wrong by forcing a colleague calculate the same thing.
> >
> > Anyone have had same issues or is it just me? My system perhaps trying to force me to use internal metadata although I don't want to..?
> >
> > I use (still) Ubuntu 10.04.2 LTS (64bit)
> > Apt-get installed drbd8-utils drbd8-source
> > drbd8-source        2:8.3.7-1ubuntu2.1  
> > drbd8-utils         2:8.3.7-1ubuntu2.1 
> >
> > config:
> > resource nfs1 {
> >
> >         protocol C;
> >
> >         handlers {
> >                 pri-on-incon-degr "echo o > /proc/sysrq-trigger ; halt -f";
> >                 pri-lost-after-sb "echo o > /proc/sysrq-trigger ; halt -f";
> >                 local-io-error "echo o > /proc/sysrq-trigger ; halt -f";
> >                 outdate-peer "/usr/lib/heartbeat/drbd-peer-outdater -t 5";
> >         }
> >
> >         startup {
> >                 degr-wfc-timeout 120;
> >         }
> >
> >         disk {
> >                 on-io-error detach;
> >         }
> >
> >         net {
> >                 cram-hmac-alg sha1;
> >                 shared-secret "password";
> >                 after-sb-0pri disconnect;
> >                 after-sb-1pri disconnect;
> >                 after-sb-2pri disconnect;
> >                 rr-conflict disconnect;
> >         }
> >
> >         syncer {
> >                 rate 100M;
> >                 verify-alg sha1;
> >                 al-extents 257;
> >         }
> >
> >         on rix-san05-primary {
> >                 device  /dev/drbd1;
> >                 disk    /dev/sdb2;
> >                 address 192.168.100.5:7788;
> >                 meta-disk /dev/sdb1[1];
> >         }
> >
> >         on rix-san05-secondary {
> >                 device  /dev/drbd1;
> >                 disk    /dev/sdb2;
> >                 address 192.168.100.6:7788;
> >                 meta-disk /dev/sdb1[1];
> >         }
> > }
> >
> > Regards
> > Mikael Andersson
> >
> 
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-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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