If you shut down the computer gracefully first before you power the disks off it should be ok more often than not, but you really should try to have everything on the same system so this can all be coordinated by the OS and the hardware.
As others have said, avoid powering the disks off before the OS has had a chance to shut down or your disks will NOT be in a recoverable state when everything comes back online.
I’m not even sure the setup you are describing would benefit at all from a different storage method, even “regular” writes could be in memory or controller buffers. External drives are not meant to have their power cut.
If you shut down the computer gracefully first before you power the disks off it should be ok more often than not, but you really should try to have everything on the same system so this can all be coordinated by the OS and the hardware.
As others have said, avoid powering the disks off before the OS has had a chance to shut down or your disks will NOT be in a recoverable state when everything comes back online.
I’m not even sure the setup you are describing would benefit at all from a different storage method, even “regular” writes could be in memory or controller buffers. External drives are not meant to have their power cut.