From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chandra Seetharaman Subject: SCSI Hardware Handler and slow failover with large number of LUNS Date: Sat, 04 Apr 2009 14:30:36 -0700 Message-ID: <1238880636.11478.8.camel@chandra-ubuntu> Reply-To: sekharan@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from e34.co.us.ibm.com ([32.97.110.152]:53597 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbZDDVab (ORCPT ); Sat, 4 Apr 2009 17:30:31 -0400 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e34.co.us.ibm.com (8.13.1/8.13.1) with ESMTP id n34LSGZh027474 for ; Sat, 4 Apr 2009 15:28:16 -0600 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n34LUTJX131792 for ; Sat, 4 Apr 2009 15:30:29 -0600 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n34LUS61027517 for ; Sat, 4 Apr 2009 15:30:29 -0600 Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: dm-devel , Linux SCSI Mailing list Cc: "Moger, Babu" Hello All, During testing with the latest SCSI DH Handler on a rdac storage, Babu found that the failover time with 100+ luns takes about 15 minutes, which is not good. We found that the problem is due to the fact that we serialize activate in dm on the work queue. We can solve the problem in rdac handler in 2 ways 1. batch up the activates (mode_selects) and send few of them. 2. Do mode selects in async mode. Just wondering if anybody had seen the same problem in other storages (EMC, HP and Alua). Please share your experiences, so we can come up with a solution that works for all hardware handlers. regards, chandra