Re: Unexpected raid1 behaviour

[Duncan <1i5t5.duncan@cox.net>]

Austin S. Hemmelgarn posted on Wed, 20 Dec 2017 08:33:03 -0500 as
excerpted:

>> The obvious answer is: do it via kernel command line, just like mdadm
>> does:
>> rootflags=device=/dev/sda,device=/dev/sdb
>> rootflags=device=/dev/sda,device=missing
>> rootflags=device=/dev/sda,device=/dev/sdb,degraded
>> 
>> If only btrfs.ko recognized this, kernel would be able to assemble
>> multivolume btrfs itself. Not only this would allow automated degraded
>> mounts, it would also allow using initrd-less kernels on such volumes.
> Last I checked, the 'device=' options work on upstream kernels just
> fine, though I've never tried the degraded option.  Of course, I'm also
> not using systemd, so it may be some interaction with systemd that's
> causing them to not work (and yes, I understand that I'm inclined to
> blame systemd most of the time based on significant past experience with
> systemd creating issues that never existed before).

Has the bug where rootflags=device=/dev/sda1,device=/dev/sdb1 failed, 
been fixed?  Last I knew (which was ancient history in btrfs terms, but 
I've not seen mention of a patch for it in all that time either), device= 
on the userspace commandline worked, and device= on the kernel commandline 
worked if there was just one device, but it would fail for more than one 
device.  Mounting degraded (on a pair-device raid1) would then of course 
work, since it would just use the one device=, but that's simply 
dangerous for routine use regardless of whether it actually assembled or 
not, thus effectively forcing an initr* for multi-device btrfs root in 
ordered to get it mounted properly.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman