perfomance indicator in drbd

The second line of /proc/drbd information for each resource contains the following counters and gauges:

ns (network send). Volume of net data sent to the partner via the network connection; in Kibyte.

nr (network receive). Volume of net data received by the partner via the network connection; in Kibyte.

dw (disk write). Net data written on local hard disk; in Kibyte.

dr (disk read). Net data read from local hard disk; in Kibyte.

al (activity log). Number of updates of the activity log area of the meta data.

bm (bit map). Number of updates of the bitmap area of the meta data.

lo (local count). Number of open requests to the local I/O sub-system issued by DRBD.

pe (pending). Number of requests sent to the partner, but that have not yet been answered by the latter.

ua (unacknowledged). Number of requests received by the partner via the network connection, but that have not yet been answered.

ap (application pending). Number of block I/O requests forwarded to DRBD, but not yet answered by DRBD.

ep (epochs). Number of epoch objects. Usually 1. Might increase under I/O load when using either the barrier or the none write ordering method.

wo (write order). Currently used write ordering method: b(barrier), f(flush), d(drain) or n(none).

oos (out of sync). Amount of storage currently out of sync; in Kibibytes.