It’s doable with a swap file instead. But some filesystems are more supportive than others.
For example BTRFS doesn’t support swapfiles over multiple devices (so my raid1c3 spanning 3 differently sized disks for example) and also swapfiles must be completely pre-allocated.
And no matter the filesystem you need to manually tell the kernel device and physical offset for the file via kernel parameters. Which can again be easier on some than on others (also causing the no-multiple-device filesystem problem mentioned above.
btrfs’s handling makes sense. The kernel talks to the disk directly, the file is just a pointer for what range it uses, and a placeholder for the filesystem. Something like raid, balancing, cow, all won’t work because the kernel doesn’t even go through btrfs to change the swap"file".
If you want a proper file as swapfile, with the corresponding overhead, you can make a regular file and mount it via loopback then use it as a swap device.
It’s doable with a swap file instead. But some filesystems are more supportive than others.
For example BTRFS doesn’t support swapfiles over multiple devices (so my raid1c3 spanning 3 differently sized disks for example) and also swapfiles must be completely pre-allocated.
And no matter the filesystem you need to manually tell the kernel device and physical offset for the file via kernel parameters. Which can again be easier on some than on others (also causing the no-multiple-device filesystem problem mentioned above.
btrfs’s handling makes sense. The kernel talks to the disk directly, the file is just a pointer for what range it uses, and a placeholder for the filesystem. Something like raid, balancing, cow, all won’t work because the kernel doesn’t even go through btrfs to change the swap"file".
If you want a proper file as swapfile, with the corresponding overhead, you can make a regular file and mount it via loopback then use it as a swap device.