The I/O usage is high on virtual drives of drdb, but the usage is very low on the underlying drive. Is it right to ignore usage of I/O on virtual drive as the underlying disk usage is fine.

We have 4 Redhat Boxes Dell PowerEdge R630 (say a,b,c,d) having the following OS/packages.

RedHat EL 6.5 MySql Enterprise 5.6 DRBD 8.4 Corosync 1.4.7

We have setup 4-way stacked drbd resources as below:

Cluster Cluster-1: servers a and b connected to each other local lan Cluster Cluster-2: servers c and d

Cluster Cluster-1 and Cluster-2 are attached via stacked drbd via virtual IPs and are part of different data centres.

The drbd0 disks have been created locally on each servers 1GB, and are further attached to drbd10.

underlying Disk usage that is normal:-

 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda2 0.00 3718.00 0.00 441.00 0.00 33268.00 75.44 0.06 0.13 0.08 3.35 avg-cpu: %user %nice %system %iowait %steal %idle 1.25 0.00 0.81 1.75 0.00 96.18 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda2 0.00 1242.00 0.00 133.50 0.00 11008.00 82.46 0.02 0.17 0.11 1.45 

The Virtual drive I/O usage that is high during the same time:-

Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util drbd10 0.00 0.00 0.00 23.50 0.00 188.00 8.00 3.41 6.11 38.17 89.70 avg-cpu: %user %nice %system %iowait %steal %idle 24.42 0.00 0.69 0.06 0.00 74.83 

For checking the I/O usage for DRBD, which drive should we be monitoring??

On googling i found this link:- http://lists.linbit.com/pipermail/drbd-user/2012-January/017622.html