@yuhunglin Good point. MD5 is faster but SHA1 is more collision-resistant. Both are inappropriate for security usages, but that's not relevant here. 

I ran this on dev-01:
openssl speed sha1 md5
The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
md5              52949.39k   160605.97k   366902.21k   537368.83k   627556.68k
sha1             57445.29k   162032.61k   343557.93k   477243.59k   542551.50k