On 08/19/2013 05:16 AM, Timo Veith wrote: > Hello open-iscsi members, > > could someone give me a hint where to find more about the reason why the > mentioned iscsi error appears? > > We are doing benchmarks with fio and the following errors occurs after > some time. The monitoring interface of the iscsi target appliance > suddenly shows no more throughput for about 20secs to 2 minutes. Then > throughput starts again. > > The same errors also appear with a huge database import (postgresql). So > it is probably not related to fio but more to heavy i/o. > > /var/log/messages: > > Aug 16 16:47:45 ibs-mngr2 kernel: [80500.790747] connection15:0: > detected conn error (1021) > Aug 16 16:47:46 ibs-mngr2 iscsid: Kernel reported iSCSI connection 15:0 > error (1021 - ISCSI_ERR_SCSI_EH_SESSION_RST: S > ession was dropped as a result of SCSI error recovery) state (3) > Aug 16 16:47:49 ibs-mngr2 iscsid: connection15:0 is operational after > recovery (1 attempts)
The scsi layer sets a timeout for each command. I think the default is 30 or 60 secs in SLES 11. If a command does not complete within that timeout, the scsi error handler runs. The scsi eh basically calls the iscsi eh callouts to try and abort commands then restart them. If it cannot abort them it tries lun and target resets and if those fail we end up dripping the session and relogging in. So that is what is happening here. You are probably sending too many commands to the device. Either the storage cannot handle them or the connection is too slow or some combo of both. Since you have 10 gig ethernet it is probably that the device is too slow. You would want to check your target's logs and see if there are any errors during this time. If not then lower the queue depth on the initiator side (see the iscsi node.session.queue_depth and node.session.cmds_max params) or increase the scsi command timeout via udev or sysfs (however SUSE reccomends). -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to open-iscsi+unsubscr...@googlegroups.com. To post to this group, send email to open-iscsi@googlegroups.com. Visit this group at http://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/groups/opt_out.
