[DRBD-user] PROBLEM:"Digest mismatch, buffer modified by upper layers during write" happend again and again

Lars Ellenberg lars.ellenberg at linbit.com
Fri Mar 28 10:30:17 CET 2014

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

On Fri, Mar 28, 2014 at 04:37:53PM +0800, 活在梦中 wrote:
> hI:   i am from china,i have a  some serious problem with my drbd,we
> did a ha for our mysql database with drbd ,everything is ok when we
> did not use NIC bond,but when we bond the nic with mode
> 1(active-backup),the link between the drbd perfom strange,just
> disconect-unknown-connect,following is the log:
> ------------------------------

Please read

And the links therein:
| http://www.gossamer-threads.com/lists/drbd/users/21069#21069
| The Problem:
| http://lwn.net/Articles/429305/
| http://thread.gmane.org/gmane.linux.kernel/1103571
| http://thread.gmane.org/gmane.linux.scsi/59259

> Mar 27 13:57:58 mysql03 kernel: block drbd0: updated sync UUID B0A60E84594BD05F:9C83E27AB8FC9A75:9C82E27AB8FC9A75:9C81E27AB8FC9A75
> Mar 27 13:57:58 mysql03 kernel: block drbd0: Digest mismatch, buffer modified by upper layers during write: 999570272s +4096

DRBD is simply detecting that your application layers keep modifying data,
even while it is in-flight to the storage backend.
So the result of that write is undefined (would it hit stable storage
with the data when submitted, or any intermediate state, as the data
keeps being modified, or what?)

So you either tell DRBD to ignore that (disable data-integrity checksumming)
And/or you fix your application and/or file system and/or operating system
to not modify data that is in-flight to the storage (keyword: stable pages).
Or you live with the symptoms you are seing.

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

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