From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: SCSI's heuristics for enabling WRITE SAME still need work [was: dm mpath: disable WRITE SAME if it fails] Date: Tue, 24 Sep 2013 11:37:20 +0200 Message-ID: <52415D50.508@redhat.com> References: <20130919161043.GA27081@redhat.com> <20130920212142.GA17898@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-qe0-f51.google.com ([209.85.128.51]:52876 "EHLO mail-qe0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752778Ab3IXJhG (ORCPT ); Tue, 24 Sep 2013 05:37:06 -0400 Received: by mail-qe0-f51.google.com with SMTP id ne12so2981312qeb.10 for ; Tue, 24 Sep 2013 02:37:06 -0700 (PDT) In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Martin K. Petersen" Cc: Mike Snitzer , dm-devel@redhat.com, linux-scsi@vger.kernel.org Il 21/09/2013 00:03, Martin K. Petersen ha scritto: > > The major headache here of course is that WRITE SAME is inherently > destructive. We can't just fire off one during discovery and see if it > works. For WRITE you can issue a command with a transfer length of 0 to > see if things work. But unfortunately for WRITE SAME a transfer length > of zero means "wipe the entire device". Yikes! What about WRITE SAME with an out-of-range lba? Or lba equal to the size of the disk and #blocks equal to zero. Paolo