11.5 hours is an unacceptable runtime considering running on a production server. It should be borne in mind that beforehand I try to stop all running daemons and services.
Yes, i don't need to have exact 1:1 clones across disk sectors.
It is strange that a port utility similar to the old clonehdd has not been written, using the standard dump, restore, gpart tools to work in the modern FreeBSD environment((
Judging by the output of your df command given above, this is probably an 8TB disk (the file systems listed there add up to 7.2TB). With perfect tools, you can read or write a disk at about 150...200 MB/second. Long division tells us that copying an 8TB disk will take between 11.1 and 14.8 hours, assuming those IO rates. In reality, those IO rates are somewhat difficult to accomplish; you need to use large IOs (512 bytes of 4KiB is out, I would recommend 1MiB and up), you need to overlap reads and writes (so both disks are simultaneously busy), and for best performance you need to have multiple outstanding writes at all times. If you got 11.5 hours, you are doing very well.
What this really points out is that doing image (byte accurate) copies of disks can be very inefficient, if the source file systems are quite empty (which is the case in your situation, judging by the df output). Theoretically, something like dump and restore would be a lot faster in this situation (since most of the disk is unallocated, and doesn't need to be copied). But note that this is specific to your situation of mostly empty file systems on the source disk; if instead the file systems were mostly full, then a byte-wise copy using very large IOs would be significantly faster, because the disk would be used sequentially and queued, not random. The exact cutover point for this tradeoff is hard to guess, and depends on specifics (like disk technology and file system fragmentation).
Why has nobody implemented such as tool recently? Don't know. This kind of copy can be relatively easily done by hand: Partition the target disk according to your tastes. Then iterate over all source file systems. If the source is pretty full, and the target partition the same size or larger than the source partition, use a good binary copy tool (dd is decent but not perfect, a multi-threaded one can be hacked up in an afternoon in C or python) to perform an image copy. If the target partition is larger than the source, use the standard commands to resize the target file system afterwards. On the other hand, if the source is pretty empty, then perform mkfs on the target partition, and use dump/restore to copy the data.
