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 almost 10 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.