From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: [LSF/MM TOPIC] Reducing the SRP initiator failover time Date: Fri, 01 Feb 2013 14:43:38 +0100 Message-ID: <510BC68A.90708@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from jacques.telenet-ops.be ([195.130.132.50]:44228 "EHLO jacques.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755099Ab3BANnm (ORCPT ); Fri, 1 Feb 2013 08:43:42 -0500 Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: lsf-pc@lists.linux-foundation.org, linux-scsi , "linux-rdma@vger.kernel.org" , David Dillow It is known that it takes about two to three minutes before the upstream SRP initiator fails over from a failed path to a working path. This is not only considered longer than acceptable but is also longer than other Linux SCSI initiators (e.g. iSCSI and FC). Progress so far with improving the fail-over SRP initiator has been slow. This is because the discussion about candidate patches occurred at two different levels: not only the patches itself were discussed but also the approach that should be followed. That last aspect is easier to discuss in a meeting than over a mailing list. Hence the proposal to discuss SRP initiator failover behavior during the LSF/MM summit. The topics that need further discussion are: * If a path fails, remove the entire SCSI host or preserve the SCSI host and only remove the SCSI devices associated with that host ? * Which software component should test the state of a path and should reconnect to an SRP target if a path is restored ? Should that be done by the user space process srp_daemon or by the SRP initiator kernel module ? * How should the SRP initiator behave after a path failure has been detected ? Should the behavior be similar to the FC initiator with its fast_io_fail_tmo and dev_loss_tmo parameters ? Dave, if this topic gets accepted, I really hope you will be able to attend the LSF/MM summit. Bart.