[DRBD-user] mke2fs issues an unused block warning when creating drbd0

Dischino, Chris cdischino at sonusnet.com
Wed Dec 9 17:13:15 CET 2015

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


On a VM,  when we go to create the drbd0 file system,  mke2fs writes out a warning,47 blocks unused.  Using tune2fs -l, both drbd0, and the physical device sda6,  have a block count of 14909440  and a block size of 4096.  From my calculations below,  it looks like  drbd meta data has included the 47 unused blocks and the file system has not.  I have never seen "warning: 47 blocks unused" message before.  Not sure if it is related to the VM, the size of the partition.  Does anyone know what this warning is trying to tell me ?  Any thought on why mke2fs would not use all the blocks ?  No bad blocks were detected.  When I calculate the size of the meta data, it seem to include the unused blocks, do you know if this is correct ?  Do  I need to specify the number of blocks for this case, when creating the drbd device ? Any information would be greatly appreciated.
/Chris
Sonus Networks

ERROR:local drbd fs mismatch MetaData 59637948 sda6 59637760 drbd0 59637760

Writing meta data...
initializing activity log
NOT initialized bitmap
New drbd meta data block successfully created.
[root at SUZUKA05 sonus]# sleep 1
[root at SUZUKA05 sonus]# /sbin/service drbd start
[....] Starting DRBD resources:[ d(mirror) s(mirror) n(mirror) ]. ok
[root at SUZUKA05 sonus]# /sbin/drbdadm -- --overwrite-data-of-peer primary mirror
[root at SUZUKA05 sonus]# /sbin/mke2fs -j /dev/drbd0 | colcrt -  2> /tmp/cld.txt
mke2fs 1.42.5 (29-Jul-2012)
warning: 47 blocks unused.
Filesystem label=
OS type: Linux
Block size=4096 (log=2)

root at SUZUKA05 sonus]# cat /proc/partitions
major minor  #blocks  name
   8        6   59639808 sda6
147      0   59637948 drbd0

[root at SUZUKA05 sonus]# expr $((((14909440+47)*4096)/1024))
59637948
[root at SUZUKA05 sonus]# expr $((((14909440+0)*4096)/1024))
59637760
[root at SUZUKA05 sonus]# expr $((59637948-59637760))
188
[root at SUZUKA05 sonus]# expr $(((47*4096)/1024))
188



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