I'm seeing disk detection order changing across reboots on 5.x kernels (5.4, 5.10, 5.14), but not 4.9, 4.14, 4.19, with megaraid_sas (Dell PERC_H700). With 13 disks and 5.14.14, the order changes almost always. I did initially try to bisect this issue, but it seems to become more rare in earlier kernels, and there are some non-booting problems between 4.x and 5.x. The most common effect is swapping of sda with sdb, or two neighboring devices in the list; for example: # diff -u lsblk-S-5.10.0 lsblk-S-5.10.0-2 --- lsblk-S-5.10.0 2021-11-04 15:23:23.767008360 -0400 +++ lsblk-S-5.10.0-2 2021-11-04 17:34:37.748310196 -0400 @@ -1,6 +1,6 @@ NAME HCTL TYPE VENDOR MODEL REV TRAN -sda 0:2:0:0 disk DELL PERC_H700 2.10 -sdb 0:2:2:0 disk DELL PERC_H700 2.10 +sda 0:2:2:0 disk DELL PERC_H700 2.10 +sdb 0:2:0:0 disk DELL PERC_H700 2.10 sdc 0:2:3:0 disk DELL PERC_H700 2.10 sdd 0:2:4:0 disk DELL PERC_H700 2.10 sde 0:2:5:0 disk DELL PERC_H700 2.10 This is happening on vendor (Debian 5.10.0) and home-built kernels, and on a variety of hosts. On all kernels, the detection printks come up in an interesting order, but in older kernels, it always ends up with an sd-name that is ordered by SCSI ID ascending: [ 2.289776] sd 0:2:0:0: [sda] 999030784 512-byte logical blocks: (512 GB/476 GiB) [ 2.289918] sd 0:2:4:0: [sdd] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) [ 2.289947] sd 0:2:3:0: [sdc] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) [ 2.290032] sd 0:2:6:0: [sdf] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) [ 2.290210] sd 0:2:7:0: [sdg] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) [ 2.290248] sd 0:2:9:0: [sdi] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) [ 2.290323] sd 0:2:2:0: [sdb] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) [ 2.290461] sd 0:2:5:0: [sde] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) [ 2.290476] sd 0:2:8:0: [sdh] 11719933952 512-byte logical blocks: (6.00 TB/5.46 TiB) Full "dmesg" is saved here: https://0x.ca/sim/ref/5.10.0/dmesg Any ideas on suggestions on what I could use to track down what changed here, or ideas on what might have influenced it? Simon-
