md5-vs-redis-bench.rb

require 'benchmark'
require 'redis'
require 'digest/md5'

n = 10000
redis = Redis.new

Benchmark.bm do |bm|
  bm.report do
    n.times { Digest::MD5.hexdigest 'christopher.lloyd@gmail.com' }
  end

  redis.set 'benchmark:gravatastic',
            Digest::MD5.hexdigest('christopher.lloyd@gmail.com')

  bm.report do
    n.times { redis.get 'benchmark:gravatastic' }
  end

end

stdout

      user     system      total        real
  0.020000   0.000000   0.020000 (  0.026320)
  0.390000   0.280000   0.670000 (  1.691016)