kid3/kid2 hard disks: current state

/dev/sdc6         101253   7981     88106   9% /
/dev/sdc3         111493    126    111368   1% /videos
/dev/sdc2         218500  48874    169627  23% /windows
/dev/sda1        1907729 873821   1032357  46% /home

/dev/sdc is the original Windows/Linux boot/Swap disk and has the root in sdc6:

Device     Boot     Start       End   Sectors   Size Id Type
/dev/sdc1              63  81835109  81835047    39G 27 Hidden NTFS WinRE
/dev/sdc2  *     81836032 529324031 447488000 213,4G  6 FAT16
/dev/sdc3       529324032 757660408 228336377 108,9G  7 HPFS/NTFS/exFAT
/dev/sdc4       757661694 976771071 219109378 104,5G  5 Extended
/dev/sdc5       968599552 976771071   8171520   3,9G 82 Linux swap / Solaris
/dev/sdc6       757661696 968599551 210937856 100,6G 83 Linux

/dev/sda is a single btrfs drive, on the 2TB that came from base:
Device     Boot Start        End    Sectors  Size Id Type
/dev/sda1        2048 3907029167 3907027120  1,8T 83 Linux


/dev/sdb is currently unused and contains:
Device     Boot     Start        End    Sectors   Size Id Type
/dev/sdb1            2048  976575284  976573237 465,7G 83 Linux
/dev/sdb2       976576512 3907029167 2930452656   1,4T 8e Linux LVM

/dev/sdb1 and /dev/sdc3 are empty; sdb2 is the old /home LVM that didn't mount very well lately.  So /dev/sdb is essentially free to be reused to extend the btrfs, or move to kid2 (the new backup server with urBackup).

But extending kid3's home directory is not urgent (currently not yet 50% used and could probably be cleaned too).  On kid2, the btrfs for urBackup is not under stress either, with 1.10 TB used on 3 drives, including one 2TB drive that could be enough to hold everything anyway.

So I decide to not decide doing anything right now.  Maybe I could free the 2 extra drives in kid2 as they're small capacity and could be reused to revive an old laptop or so:
 
sudo btrfs device remove /dev/sdc1 /var/backup/urBackup/

So the above command did take a while, but ended up freeing /dev/sdc1 which is the 500GB hard drive that I bought for 5€.  The 640GB that remains can't be freed for the moment as it is part of the RAID1 profile.  So now I'm planning to add the 2TB drive to this:

Label: none  uuid: 4881245e-bed5-4526-b9ff-3b5ba39b283d
    Total devices 2 FS bytes used 1.10TiB
    devid    3 size 596.17GiB used 567.03GiB path /dev/sda1
    devid    4 size 1.82TiB used 567.03GiB path /dev/sdd


and when done I could easily remove the sda1 small drive.