From: "Ewan D. Milne" <emilne@redhat.com> To: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>, erwin@erwinvanlonden.net, martin.petersen@oracle.com, martin.wilck@suse.com, hare@suse.de Cc: dgilbert@interlog.com, jejb@linux.vnet.ibm.com, "systemd-devel@lists.freedesktop.org" <systemd-devel@lists.freedesktop.org>, hch@lst.de, dm-devel@redhat.com, hare@suse.com, linux-scsi@vger.kernel.org Subject: Re: Antw: [EXT] Re: [dm-devel] RFC: one more time: SCSI device identification Date: Tue, 27 Apr 2021 16:04:19 -0400 [thread overview] Message-ID: <731ece1c29243937c52ecdb1a3823d4fccd17bd1.camel@redhat.com> (raw) In-Reply-To: <6087ECF1020000A100040C7F@gwsmtp.uni-regensburg.de> On Tue, 2021-04-27 at 12:52 +0200, Ulrich Windl wrote: > > > > Hannes Reinecke <hare@suse.de> schrieb am 27.04.2021 um 10:21 > > > > in Nachricht > > <2a6903e4-ff2b-67d5-e772-6971db8448fb@suse.de>: > > On 4/27/21 10:10 AM, Martin Wilck wrote: > > > On Tue, 2021‑04‑27 at 13:48 +1000, Erwin van Londen wrote: > > > > > > > > > > Wrt 1), we can only hope that it's the case. But 2) and 3) > > > > > need work, > > > > > afaics. > > > > > > > > > > > > > In my view the WWID should never change. > > > > > > In an ideal world, perhaps not. But in the dm‑multipath realm, we > > > know > > > that WWID changes can happen with certain storage arrays. See > > > https://listman.redhat.com/archives/dm‑devel/2021‑February/msg00116.html > > > > > > and follow‑ups, for example. > > > > > > > And it's actually something which might happen quite easily. > > The storage array can unmap a LUN, delete it, create a new one, and > > map > > that one into the same LUN number than the old one. > > If we didn't do I/O during that interval upon the next I/O we will > > be > > getting the dreaded 'Power‑On/Reset' sense code. > > _And nothing else_, due to the arcane rules for sense code > > generation in > > SAM. > > But we end up with a completely different device. > > > > The only way out of it is to do a rescan for every POR sense code, > > and > > disable the device eg via DID_NO_CONNECT whenever we find that the > > identification has changed. We already have a copy of the original > > VPD > > page 0x83 at hand, so that should be reasonably easy. > > I don't know the depth of the SCSI or FC protocol, but storage > systems > typically signal such events, maybe either via some unit attention or > some FC > event. Older kernels logged that there was a change, but a manual > SCSI bus scan > is needed, while newer kernels find new devices "automagically" for > some > products. The HP EVA 6000 series wored that way, a 3PAR SotorServ > 8000 series > also seems to work that way, but not Pure Storage X70 R3. FOr the > latter you > need something like a FC LIP to make the kernel detect the new > devices (LUNs). > I'm unsure where the problem is, but in principle the kernel can be > notified... There has to be some command on which the Unit Attention status can be returned. (In a multipath configuration, the path checker commands may do this). In absence of a command, there is no asynchronous mechanism in SCSI to report the status. On FC things related to finding a remote port will trigger a rescan. -Ewan > > > > > I had a rather lengthy discussion with Fred Knight @ NetApp about > > Power‑On/Reset handling, what with him complaining that we don't > > handle > > is correctly. So this really is something we should be looking > > into, > > even independently of multipathing. > > > > But actually I like the idea from Martin Petersen to expose the > > parsed > > VPD identifiers to sysfs; that would allow us to drop sg_inq > > completely > > from the udev rules. > > Talking of VPDs: Somewhere in the last 12 years (within SLES 11)there > was a > kernel change regarding trailing blanks in VPD data. That change blew > up > several configurations being unable to re-recognize the devices. In > one case > the software even had bound a license to a specific device with > serial number, > and that software found "new" devices while missing the "old" ones... > > Regards, > Ulrich > > > > > Cheers, > > > > Hannes > > ‑‑ > > Dr. Hannes Reinecke Kernel Storage Architect > > hare@suse.de +49 911 74053 > > 688 > > SUSE Software Solutions Germany GmbH, 90409 Nürnberg > > GF: F. Imendörffer, HRB 36809 (AG Nürnberg) > > >
WARNING: multiple messages have this Message-ID (diff)
From: "Ewan D. Milne" <emilne@redhat.com> To: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>, erwin@erwinvanlonden.net, martin.petersen@oracle.com, martin.wilck@suse.com, hare@suse.de Cc: hare@suse.com, "systemd-devel@lists.freedesktop.org" <systemd-devel@lists.freedesktop.org>, linux-scsi@vger.kernel.org, dm-devel@redhat.com, dgilbert@interlog.com, jejb@linux.vnet.ibm.com, hch@lst.de Subject: Re: [dm-devel] Antw: [EXT] Re: RFC: one more time: SCSI device identification Date: Tue, 27 Apr 2021 16:04:19 -0400 [thread overview] Message-ID: <731ece1c29243937c52ecdb1a3823d4fccd17bd1.camel@redhat.com> (raw) In-Reply-To: <6087ECF1020000A100040C7F@gwsmtp.uni-regensburg.de> On Tue, 2021-04-27 at 12:52 +0200, Ulrich Windl wrote: > > > > Hannes Reinecke <hare@suse.de> schrieb am 27.04.2021 um 10:21 > > > > in Nachricht > > <2a6903e4-ff2b-67d5-e772-6971db8448fb@suse.de>: > > On 4/27/21 10:10 AM, Martin Wilck wrote: > > > On Tue, 2021‑04‑27 at 13:48 +1000, Erwin van Londen wrote: > > > > > > > > > > Wrt 1), we can only hope that it's the case. But 2) and 3) > > > > > need work, > > > > > afaics. > > > > > > > > > > > > > In my view the WWID should never change. > > > > > > In an ideal world, perhaps not. But in the dm‑multipath realm, we > > > know > > > that WWID changes can happen with certain storage arrays. See > > > https://listman.redhat.com/archives/dm‑devel/2021‑February/msg00116.html > > > > > > and follow‑ups, for example. > > > > > > > And it's actually something which might happen quite easily. > > The storage array can unmap a LUN, delete it, create a new one, and > > map > > that one into the same LUN number than the old one. > > If we didn't do I/O during that interval upon the next I/O we will > > be > > getting the dreaded 'Power‑On/Reset' sense code. > > _And nothing else_, due to the arcane rules for sense code > > generation in > > SAM. > > But we end up with a completely different device. > > > > The only way out of it is to do a rescan for every POR sense code, > > and > > disable the device eg via DID_NO_CONNECT whenever we find that the > > identification has changed. We already have a copy of the original > > VPD > > page 0x83 at hand, so that should be reasonably easy. > > I don't know the depth of the SCSI or FC protocol, but storage > systems > typically signal such events, maybe either via some unit attention or > some FC > event. Older kernels logged that there was a change, but a manual > SCSI bus scan > is needed, while newer kernels find new devices "automagically" for > some > products. The HP EVA 6000 series wored that way, a 3PAR SotorServ > 8000 series > also seems to work that way, but not Pure Storage X70 R3. FOr the > latter you > need something like a FC LIP to make the kernel detect the new > devices (LUNs). > I'm unsure where the problem is, but in principle the kernel can be > notified... There has to be some command on which the Unit Attention status can be returned. (In a multipath configuration, the path checker commands may do this). In absence of a command, there is no asynchronous mechanism in SCSI to report the status. On FC things related to finding a remote port will trigger a rescan. -Ewan > > > > > I had a rather lengthy discussion with Fred Knight @ NetApp about > > Power‑On/Reset handling, what with him complaining that we don't > > handle > > is correctly. So this really is something we should be looking > > into, > > even independently of multipathing. > > > > But actually I like the idea from Martin Petersen to expose the > > parsed > > VPD identifiers to sysfs; that would allow us to drop sg_inq > > completely > > from the udev rules. > > Talking of VPDs: Somewhere in the last 12 years (within SLES 11)there > was a > kernel change regarding trailing blanks in VPD data. That change blew > up > several configurations being unable to re-recognize the devices. In > one case > the software even had bound a license to a specific device with > serial number, > and that software found "new" devices while missing the "old" ones... > > Regards, > Ulrich > > > > > Cheers, > > > > Hannes > > ‑‑ > > Dr. Hannes Reinecke Kernel Storage Architect > > hare@suse.de +49 911 74053 > > 688 > > SUSE Software Solutions Germany GmbH, 90409 Nürnberg > > GF: F. Imendörffer, HRB 36809 (AG Nürnberg) > > > -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel
next prev parent reply other threads:[~2021-04-27 20:04 UTC|newest] Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-29 9:58 RFC: one more time: SCSI device identification Martin Wilck 2021-03-29 9:58 ` [dm-devel] " Martin Wilck 2021-04-06 4:47 ` Martin K. Petersen 2021-04-06 4:47 ` [dm-devel] " Martin K. Petersen 2021-04-16 23:28 ` Martin Wilck 2021-04-16 23:28 ` [dm-devel] " Martin Wilck 2021-04-22 2:46 ` Martin K. Petersen 2021-04-22 2:46 ` [dm-devel] " Martin K. Petersen 2021-04-22 9:07 ` Martin Wilck 2021-04-22 9:07 ` [dm-devel] " Martin Wilck 2021-04-22 16:14 ` Benjamin Marzinski 2021-04-22 16:14 ` [dm-devel] " Benjamin Marzinski 2021-04-23 1:40 ` Martin K. Petersen 2021-04-23 1:40 ` [dm-devel] " Martin K. Petersen 2021-04-23 10:28 ` Martin Wilck 2021-04-23 10:28 ` [dm-devel] " Martin Wilck 2021-04-26 11:14 ` Antw: [EXT] Re: [systemd-devel] " Ulrich Windl 2021-04-26 11:14 ` [dm-devel] " Ulrich Windl 2021-04-26 13:16 ` Martin Wilck 2021-04-26 13:16 ` [dm-devel] " Martin Wilck 2021-04-27 3:48 ` Erwin van Londen 2021-04-27 7:02 ` Antw: [EXT] " Ulrich Windl 2021-04-27 7:02 ` [dm-devel] Antw: [EXT] " Ulrich Windl 2021-04-27 8:10 ` [dm-devel] " Martin Wilck 2021-04-27 8:10 ` Martin Wilck 2021-04-27 8:21 ` Hannes Reinecke 2021-04-27 8:21 ` Hannes Reinecke 2021-04-27 10:52 ` Antw: [EXT] " Ulrich Windl 2021-04-27 10:52 ` [dm-devel] Antw: [EXT] " Ulrich Windl 2021-04-27 20:04 ` Ewan D. Milne [this message] 2021-04-27 20:04 ` Ewan D. Milne 2021-05-04 7:32 ` Antw: [EXT] Re: [dm-devel] " Hannes Reinecke 2021-05-04 7:32 ` [dm-devel] Antw: [EXT] " Hannes Reinecke 2021-04-28 1:01 ` [dm-devel] " Erwin van Londen 2021-04-28 6:34 ` Martin Wilck 2021-04-28 6:34 ` Martin Wilck 2021-04-29 14:47 ` Erwin van Londen 2021-04-29 14:47 ` Erwin van Londen 2021-04-27 20:14 ` Ewan D. Milne 2021-04-27 20:14 ` [dm-devel] " Ewan D. Milne 2021-04-27 20:33 ` Martin Wilck 2021-04-27 20:33 ` [dm-devel] " Martin Wilck 2021-04-27 20:41 ` Ewan D. Milne 2021-04-27 20:41 ` [dm-devel] " Ewan D. Milne 2021-04-28 0:09 ` Erwin van Londen 2021-04-30 23:44 ` Ewan D. Milne 2021-05-03 2:34 ` Erwin van Londen 2021-05-03 2:34 ` Erwin van Londen 2021-04-28 6:30 ` [systemd-devel] " Martin Wilck 2021-04-28 6:30 ` [dm-devel] " Martin Wilck
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