Re: Unreliable disk detection order in 5.x

[Simon Kirby <sim@hostway.ca>]

On Fri, Nov 05, 2021 at 04:45:53PM +0900, Damien Le Moal wrote:

> > Any ideas on suggestions on what I could use to track down what changed
> > here, or ideas on what might have influenced it?
> 
> Most distro kernels are now compiled with asynchronous device scan enabled to
> speedup the boot process. This potentially result in the device names changing
> across reboots. Reliable device names are provided by udev under
> /dev/disk/by-id, by-uuid etc.
> 
> You can turn off scsi asynchronous device scan using the scsi_mod.scan=sync
> kernel boot argument, or disable the CONFIG_SCSI_SCAN_ASYNC option for your
> kernel (device drivers -> scsi device support -> asynchronous scsi scanning).
> 
> But even with synchronous scanning, device names are not reliable and there are
> no guarantees that one particular device will always have the same name.

This occurs regardless of the CONFIG_SCSI_SCAN_ASYNC setting, and also
with scsi_mod.scan=sync on vendor kernels. All of these disks are coming
from the same driver and card.

I understand that using UUIDs, by-id, etc., is an option to work around
this, but then we would have to push IDs for disks in every server to our
configuration management. It does not seem that this change is really
intentional.

Simon-