Rearraing LVM disk setup

Question

I would like to cleanup my currently tangled setup of LVM to better suit my work process. You can see I'm only using about half of the devices/storage I have available. Yet I now converted my old windows /dev/sdd1 1TB disk to also use it for linux LVM.

I'm a bit of mad man about using my disks as you can see... :-D

Current lsblk shows this:

NAME                               MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                                  8:0    0 111,8G  0 disk 
├─sda1                               8:1    0    16M  0 part 
└─sda2                               8:2    0 111,8G  0 part 
sdb                                  8:16   0 111,8G  0 disk 
└─sdb1                               8:17   0 111,8G  0 part 
  ├─vghyper-DataTwoCache_cdata     254:0    0    32G  0 lvm  
  │ └─vghyper-ArchDataTwo          254:3    0 363,4G  0 lvm  /media/DataTwo
  └─vghyper-DataTwoCache_cmeta     254:1    0    32M  0 lvm  
    └─vghyper-ArchDataTwo          254:3    0 363,4G  0 lvm  /media/DataTwo
sdc                                  8:32   0 931,5G  0 disk 
└─sdc2                               8:34   0 931,5G  0 part 
  ├─vghyper-ArchDataTwo_corig      254:2    0 363,4G  0 lvm  
  │ └─vghyper-ArchDataTwo          254:3    0 363,4G  0 lvm  /media/DataTwo
  ├─vghyper-DataOne                254:4    0   125G  0 lvm  /media/Data
  ├─vghyper-ProjectData_corig      254:8    0   100G  0 lvm  
  │ └─vghyper-ProjectData          254:9    0   100G  0 lvm  /media/Projektit
  ├─vghyper-win7                   254:11   0   100G  0 lvm  
  └─vghyper-win10                  254:12   0 111,8G  0 lvm  
sdd                                  8:48   0 931,5G  0 disk 
└─sdd1                               8:49   0 931,5G  0 part 
sde                                  8:64   0   1,8T  0 disk 
├─sde1                               8:65   0 931,5G  0 part /media/DataExt
├─sde2                               8:66   0     1G  0 part 
└─sde3                               8:67   0   100G  0 part 
nvme0n1                            259:0    0 238,5G  0 disk 
├─nvme0n1p1                        259:1    0     2G  0 part /boot
└─nvme0n1p2                        259:2    0 236,5G  0 part 
  ├─vghyper-HyperiorRoot           254:5    0   128G  0 lvm  /
  ├─vghyper-ProjectDataCache_cdata 254:6    0    32G  0 lvm  
  │ └─vghyper-ProjectData          254:9    0   100G  0 lvm  /media/Projektit
  ├─vghyper-ProjectDataCache_cmeta 254:7    0    32M  0 lvm  
  │ └─vghyper-ProjectData          254:9    0   100G  0 lvm  /media/Projektit
  └─vghyper-SwapNVMe               254:10   0    16G  0 lvm  [SWAP]

Here is some details about the device usages:

• /dev/sda is SATA SSD reserved for my win10 installation (for gaming)
• /dev/sdb is SATA SSD initialized fully for LVM PV and is used partly for lvm-cache space. It is ortherwise mosly unused.
• /dev/sdc is SATA HDD my main linux storage disk. I'm bit terrified if I lost it, especially the vghyper-ProjectData LV.
• /dev/sdd is SATA HDD now sitting idle doing nothing.
• /dev/sde is External 2TB USB3 drive for backups and small linux box installed into for recovery/travelling purposes. it has 830GB of unreserved space left.
• nvme0n1p1 is NVMe UEFI FAT32 boot partition.
• nvme0n1p2 is The Linux main PV and btrfs LV on it. Problem here is the root filesystem running tight of space. (only ~30GB free)

My goal here would be to try better gain some performance of my disks:

1. Create mirror/raid1 device from /dev/sdc and /dev/sdd (for safetly and read speed)
2. Make vghyper-ProjectData as fast as possible since I daily compile few gigs of I/O to it. Current dm-cache 32G show 99% usage.
3. Lastly use that fast NVMe/SSD space to cache the spinning rust in three levels:
   • Tier0: Linux rootfs being cached by NVMe instead of being directly on it.
   • Tier1: Misc data cached with NVMe and SSD?
   • Tier2: Regular spinning rust under dm-mirror/RAID1 for VMs

As first step I had idea that I should propably dismantle all dm-caches I currently have. (easy, done it already)

Following steps I'm not so sure about: How to build dm-mirror/RAID1 from the /dev/sdc and /dev/sdd devices without losing any data. (I'm francly terrified to touch the /dev/sdc2 PV)

How do I convert the /dev/sdc2 into RAID1/dm-mirrored device safely?