[DRBD-user] drbd writes "BUG!..." to syslog...?

Lars Ellenberg lars.ellenberg at linbit.com
Thu Nov 15 23:02:02 CET 2007

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, Nov 15, 2007 at 10:08:09PM +0100, Rudolph Bott wrote:
> Hey folks,
> 
> I stumbled over something weird in my drbd-setup:
> 
> - two boxes (actually not identical besides the whole storage subsystem and 
> the software setup)
> - debian etch, drbd 8 packages von backports.debian.org
> - standard distro kernel (2.6.18-5-686)
> - S-ATA disks, bundled in RAID-5, DRBD on top of the md-device
> - DRBD Version from /proc/drbd:
> version: 8.0.4 (api:86/proto:86)
> SVN Revision: 2947 build by root at nas01, 2007-11-08 16:36:25
> 
> 
> After a split brain situation I told the secondary to --discard-my-data and 
> did a "drbdadm connect" on both nodes
> 
> The following appeared on the primary's dmesg:
> 
> drbd0: Handshake successful: DRBD Network Protocol version 86
> drbd0: Split-Brain detected, manually solved. Sync from this node
> drbd0: peer( Unknown -> Secondary ) conn( WFReportParams -> WFBitMapS ) 
> pdsk( DUnknown -> UpToDate )
> drbd0: Writing meta data super block now.
> drbd0: BUG! md_sync_timer expired! Worker calls drbd_md_sync().
> drbd0: conn( WFBitMapS -> SyncSource ) pdsk( UpToDate -> Inconsistent )
> drbd0: Began resync as SyncSource (will sync 495616 KB [123904 bits set]).
> drbd0: Writing meta data super block now.
> 
> What exactly is this "BUG!"-line telling me here? Is that an actual problem?

it tells you that meta data io took longer than anticipated by the
developers; the "Writing meta data super block now." line shows that it
was not forgotten but just took longer than expected, so that timer
triggered.  no, normally this is not a problem.

see:

commit c1cc8577abe5b362f88f7c76b6f6308297da106c
Author: Philipp Reisner <philipp.reisner at linbit.com>
Date:   Mon Oct 15 16:59:01 2007 +0200

    Removed the "BUG!" since it is not a critical bug. Customers
    get unsettled by words like "BUG!".

diff --git a/drbd/drbd_main.c b/drbd/drbd_main.c
index b8d4751..6bf78f1 100644
--- a/drbd/drbd_main.c
+++ b/drbd/drbd_main.c
@@ -2835,7 +2835,7 @@ STATIC void md_sync_timer_fn(unsigned long data)

 STATIC int w_md_sync(drbd_dev *mdev, struct drbd_work *w, int unused)
 {
-       WARN("BUG! md_sync_timer expired! Worker calls drbd_md_sync().\n");
+       WARN("md_sync_timer expired! Worker calls drbd_md_sync().\n");
        drbd_md_sync(mdev);

        return 1;


 :-)

-- 
: 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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