[DRBD-user] Minor number count for DRBD 8.4

Bram Klein Gunnewiek bram at shockmedia.nl
Thu May 15 13:17:33 CEST 2014

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


We are upgrading our internal tools to support DRBD 8.4. When using 8.3 
we had a specific DRBD configuration in /etc/modprobe.d that set the 
minor_count to 128 e.g.:
root at testnode1:~# cat /etc/modprobe.d/drbd.conf
options drbd usermode_helper=/root/true minor_count=128

While testing out 8.4 we are unsure if the minor_count is still 
required. Using the above drbd configuration we created 131 DRBD devices 
with the folowing script:

for i in `seq 0 130`;
     lvcreate -L 4M -n drbd_test_${i} vg1
     lvcreate -L 128M -n drbd_test_${i}_meta vg1
             drbdsetup new-resource r${i}
     drbdsetup new-minor r${i} /dev/drbd${i} 0
     drbdmeta --force /dev/drbd$i v08 /dev/vg1/drbd_test_${i}_meta 0 
     drbdmeta --force /dev/drbd$i v08 /dev/vg1/drbd_test_${i}_meta 0 
     drbdsetup attach /dev/drbd$i /dev/vg1/drbd_test_$i 
/dev/vg1/drbd_test_${i}_meta 0

This worked without any errors. All disks show up in /proc/drbd:

130: cs:StandAlone ro:Secondary/Unknown ds:Inconsistent/DUnknown r-----
     ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:3840

Is the minor_count setting still valid for 8.4? I did find this 

It mentions that the maximum number of DRBD devices has changed to 
1,048,576 however I don't know if this value is default (and fixed). For 
DRBD 8.3 the default value was 32 I think thats why we have a specific 
option in the drbd kernel module of 128.

Met vriendelijke groet / Kind regards,
Bram Klein Gunnewiek | Shock Media B.V.

Tel: +31 (0)546 - 714360
Fax: +31 (0)546 - 714361
Web: https://www.shockmedia.nl/

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