Created attachment 307192 [details] Steps to Reproduce Hello, At first I noticed very strange behavior of iSCSI+MPIO. And very unexpected for me. My VM completely lost connection to iSCSI storage (all MPIO paths down), but the VM could still write data to MPIO devices in /dev/mapper/. After some digging I found that this behavior applies not only to iSCSI+MPIO, but it seems to be a feature of Device Mapper in the Linux kernel. This applies to both MPIO and LVM. I launched test VMs and checked 3 cases of this strange feature(?) of the Device Mapper: 1. LVM & dead devices - local disks offline Disabling the underlying PV disk - I can still write to LV (/dev/mapper/<vg>-<lv>) 2. MPIO & dead devices - all iSCSI MPIO paths down - transport-offline Shutting down the iSCSI server - I can still write to iSCSI MPIO devices (/dev/mapper/mpath*) 3. LVM & removed devices - local disks removed Removing the underlying PV disk - I can still write to LV (/dev/mapper/<vg>-<lv>) Details in the file attached: steps_to_reproduce.txt. Expected results: DM devices MUST return an error on write attempts when the underlying devices are down. BTW, while reading, DM returns I/O errors. -- Regards, Mirek
Sorry, I forgot to add something... >> This bugzilla is for reporting bugs against upstream Linux kernels. >> If you did not compile your own kernel from scratch, you are probably in the >> wrong place. >> Please use the following links to report a bug to your distribution instead: >> Ubuntu Yes, I know about it, but I have already reported this bug(?) to Ubuntu. That was 3 weeks ago and so far no answer, no response. You can see it here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2084979