Comment 15 for bug 1707918

For performance and benchmarks please see

https://www.percona.com/blog/2017/03/29/performance-evaluation-of-sst-data-transfer-without-encryption-part-1/
and
https://www.percona.com/blog/2017/03/30/performance-evaluation-of-sst-data-transfer-with-encryption-part-2/

Note, that xtrabackup streaming in tar format is not included into comparison because it was too slow to compete.