From mboxrd@z Thu Jan 1 00:00:00 1970 From: christophe varoqui Subject: Re: [dm-devel] [multipath] SCSI device capacity mess Date: Wed, 27 Oct 2004 21:02:39 +0200 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <1098903759.12464.32.camel@zezette> References: <1098833278.4914.24.camel@zezette> <20041027081713.GC32712@marowsky-bree.de> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from smtp5.wanadoo.fr ([193.252.22.26]:60845 "EHLO mwinf0512.wanadoo.fr") by vger.kernel.org with ESMTP id S262640AbUJ0TCl (ORCPT ); Wed, 27 Oct 2004 15:02:41 -0400 In-Reply-To: <20041027081713.GC32712@marowsky-bree.de> List-Id: linux-scsi@vger.kernel.org To: device-mapper development Cc: "linux-scsi@vger.kernel.org" > > Some SAN hardware present for a same LUN a bunch of valid paths and a > > bunch ghost paths. In my case, the ghosts responds to standard INQUIRY > > (EVPD 0x83, 0x80, ...) but the READ_CAPACITY fails : > > As a note, this is one mode the EMC CLARiiON arrays can also operate in. > Even worse, they won't present the block device at all, just the SCSI > generic mode. However, for the CLARiiONs, they can be configured to > behave sanely and reply to a READ_CAPACITY too (just all I/O will be > errored), if setting the failovermode to 1. > > I wonder whether your system can also be configured as such? > Yes it could, but it's a controler wide setting. Compatibility with other OS sharing the same controlers might impose this mode though. So I'd like to straight this situation up. > > > > 1) make the /sys/block/*/size attribute writable > > 2) resurrect a BLKSETSIZE ioctl > > 3) make device-mapper less strict, and hope we can fix the size by a > > device rescan when it get activated > > 4) sell the culprit hardware > > Personally I would opt for 4), but 3) is the likely path to solve this. > > Using the new priority group initialization code (where we sent magic > commands down to activate the newly switched-to PG) which Alasdair and I > are currently doing for the CLARiiON pampering and which provides a > plugin-architecture to the dm-mpath system, you should be able to plug > in a hardware-specific handler for your system too. > > However, "relaxing" this check should likely also be a property of the > hardware plugin loaded; I'd not wish to have it relaxed in all > scenarios. > I wonder if it's not simpler just to remove the NOSTARTONADD flag on this devices in scsi_devinfo.c. I tested that and all the READ CAPACITY succeed as expected (DEC HSG80 / COMPAQ HSV*). Wasn't this flag in part motivated by the lack of multipath support anyway ? Even in a cluster context, I don't really buy the annoyance of occasional LUN ping-pong. regards, -- christophe varoqui