can i decompress the compressed backup using option `--decompress-threads`…Is this a vaild option …?
`\$ sudo xtrabackup --decompress --parallel=16 --decompress-threads=16 --target-dir=/home/test1/vol-backup/mysql/emp --remove-original`
Yes, `--decompress-threads` is a a valid flag for xtrabackup (See docs).
As for `--parallel=16`, you may need to use copy-back as well for it to work, because that’s used for copying the files back to the datadir. (See docs).