From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: SCSI's heuristics for enabling WRITE SAME still need work [was: dm mpath: disable WRITE SAME if it fails] Date: Thu, 26 Sep 2013 10:42:00 -0400 Message-ID: References: <20130919161043.GA27081@redhat.com> <20130920212142.GA17898@redhat.com> <1379960325.4010.32.camel@localhost.localdomain> <52412581.2010909@suse.de> <20130924123449.GA16083@redhat.com> <52434D0C.1090008@fastmail.fm> <5243C880.6050609@interlog.com> <52443992.4040806@fastmail.fm> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <52443992.4040806@fastmail.fm> (Bernd Schubert's message of "Thu, 26 Sep 2013 15:41:38 +0200") Sender: linux-scsi-owner@vger.kernel.org To: Bernd Schubert Cc: dgilbert@interlog.com, "Martin K. Petersen" , Mike Snitzer , Hannes Reinecke , emilne@redhat.com, device-mapper development , linux-scsi@vger.kernel.org, Sumit.Saxena@lsi.com List-Id: dm-devel.ids >>>>> "Bernd" == Bernd Schubert writes: Bernd, Bernd> Both types of systems we have in-house neither block limits vpd Bernd> nor READ_CAP16 return anything that would indicate discard is Bernd> supported. But UNMAP and WRITE SAME unmap(*) just work fine. I have a collection of different SSDs in a tray connected to an LSI SAS2008 ASIC. The 510 is the only drive that does not have LBPME=1. Chances are it's because DRAT and RZAT are not set but it could also be that the 510 is blacklisted. Bernd> I certainly don't want to cause any more write-same trouble, but Bernd> as all layers initially have to assume write same is supported Bernd> anyway and need to dynamically disable it if it fails, can't we Bernd> also enable discard by default with WRITE SAME16 unmap? No thanks :) But you can force discards on by doing a: # echo -n unmap > /sys/class/scsi_disk/x:y:z:n/provisioning_mode or # echo -n writesame_16 > /sys/class/scsi_disk/x:y:z:n/provisioning_mode Create a udev rule if you like. In any case I wouldn't recommend using TRIM on that drive... Bernd> PS: LSI SATL with FWv17 seems to have an unmap bug - I cannot Bernd> unmap the last sector: Yes, it appears there's an off-by-one bug in the UNMAP translation. Sumit, is this something you guys can look into? -- Martin K. Petersen Oracle Linux Engineering