btrfs slow copy of 50 GB vm

[jlittle]

I've just had occasion to copy a 50 GB vm image from an SSD to NVMe, using cp. The target was a newly created btrfs. I thought it ran a bit slow, 15 ? minutes, so I dropped the btrfs, created an ext4 in the same place, and repeated the copy; 4 min 10 s. No other load at the same time in either case.

[GreyGeek]

Looks slow to me too. Why didn't you just use btrfs send & receive, since both the source and destination are btrfs subvolumes? My send & receive from my 500GB SSD to my backup 500GB SSD of the 130GB that make up my entire system takes about 15-20 seconds if I use the incremental backup switch "-p".

[oshunluvr]

It would be interesting to know if SEND is faster than copy.