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Mon, 19 Feb 2024 21:55:16 +0000 (GMT) MIME-Version: 1.0 Date: Mon, 19 Feb 2024 15:55:16 -0600 From: Wen Xiong To: Keith Busch Cc: linux-nvme@lists.infradead.org, Wenxiong , Christoph Hellwig Subject: Re: nvme native multipath question with two physical paths In-Reply-To: References: Message-ID: <03df8d694cd982973c7c2c08f1d4379a@linux.ibm.com> X-Sender: wenxiong@linux.ibm.com Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Kauz6cB0HLIJslmKSkCjKPC4I9CNazXa X-Proofpoint-GUID: Kauz6cB0HLIJslmKSkCjKPC4I9CNazXa X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-02-19_20,2024-02-19_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 lowpriorityscore=0 phishscore=0 bulkscore=0 mlxlogscore=817 mlxscore=0 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2402190164 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240219_135528_128484_077BCE32 X-CRM114-Status: GOOD ( 19.79 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 2024-02-19 13:28, Keith Busch wrote: > Nor should you see a /dev/nvme6n1 in this scenario. The mulitpath > device > doesn't change names. It assumes the identifier from the subsystem. In > your example, it uses subsystem '2' and will continue to use it no > matter which controller instances are attach to it. This feature is why > applications that have opened the /dev/nvme2n1 handle don't need to do > anything if the kernel experiences a path failover condition. > > You should see the different paths in the hidden block hierarchy, which > you can find in the sysfs directory. There should be an entry in your > example at /sys/block/nvme2c6n1/. I am pretty sure programs like > 'iostat' can show how IO is distributed among all the paths of an nvme > mulitpath device. Hi Ketith, Thanks for your detail explanation! Wendy