Thanks for the report.
  Strange. but interesting. Can you pls help to isolate...

On 01/22/2016 03:50 AM, Scott Talbert wrote:

Hi,

I'm using:

Kernel 4.2.6
btrfs-progs v4.3
Debian Wheezy

I have a RAID1 root filesystem with two devices.  When the system
initially boots up, "btrfs fi show" will show the same device twice:

Label: none  uuid: 49f7413a-99ad-41b0-8783-06c9406e2280
     Total devices 2 FS bytes used 1.19GiB
     devid    1 size 7.60GiB used 3.03GiB path /dev/sdf2
     devid    2 size 7.60GiB used 3.01GiB path /dev/sdf2

The filesystem seems to work fine (as best as I can tell) in this state.
If I then run another "btrfs device scan", it will correct itself:

Label: none  uuid: 49f7413a-99ad-41b0-8783-06c9406e2280
         Total devices 2 FS bytes used 1.19GiB
         devid    1 size 7.60GiB used 3.03GiB path /dev/sde2
         devid    2 size 7.60GiB used 3.01GiB path /dev/sdf2

Any idea what might be going on here?  On Debian it appears that the
initial "btrfs device scan" is being done by an initramfs local-premount
script where it does:

modprobe btrfs
/bin/btrfs device scan 2>/dev/null

Does there perhaps need to be some delay between inserting the kernel
module and running a scan?

May be dev1 is known as sdf initially before bootup and later when
system boots its known as sde.

I believe /boot is on non btrfs FS?

As this is a root device, Can you tell which "one" device is used for
the mount in fstab ?

Do you see the following log in the bootup logs / dmesg ?
------
printk(KERN_INFO "BTRFS: device fsid %pU devid %llu transid %llu %s %s\n",
disk_super->fsid, devid, transid, path,
ret == 2 ? "(overwritten)":"");
-------

Can you provide..
  blkid output



Thanks, Anand