zfs send/receive kills COMSTAR
We're running COMSTAR on oi_151a with the iSCSI LUNs backed by ZFS volumes. Whenever we try to back up the server, doing a zfs send/receive to the backup server, the iSCSI clients get timeout errors from the COMSTAR server. We set the tunables iscsi_sess_logging, iscsi_login_logging, idm_conn_logging, and idm_sm_logging to 1 while performing the latest zfs send/receive.
I'm including a copy of /tmp/messages with the result of the above tunables set to 1.
Updated by Dan McDonald over 8 years ago
Have you tried running "lockstat sleep 10" (or some longer snapshot of time) during the time it's hanging? I don't understand the interactions between COMSTAR and zvols as well as I'd like, but I seem to recall that COMSTAR does a lot of direct-zvol access (perhaps more than it should), and you may be seeing lock contention there.