bcache device, what size for bcahing device ?

i want to bcache a HDD partition sda4 with a nvme ssd partition

opensuse leap 15.1 partitions :

  • nvme0n1p1 / , 40 GB
  • sda1 /boot/efi , 500 MB
  • sda2 swap 8 GB
  • sda4 /home 0.9 TB

The available space in ssd is 198 GB
What size for the bcaching partition ?

Thanks

I don’t know that anyone has published a guide or even what to factor into your decision but I imagine such things like your relative read/write performance of your disks and how your data is stored and used would make every setup unique.

In any case,
The following is one article where he describes his configuration, which is 10:1

https://felixmoessbauer.com/blog-reader/tune-bcache-for-large-ssds.html

TSU