c#中 redis 和内置的 Cache 性能对比为什么差距这么大？

redis 10 万次耗时 00:00:03.9114159
Cache 10 万次耗时 00:00:00.1691259

redis 服务也是在本机运行不存在网络传输

代码
for (int i = 0; i < 100000; i++)
{
service.Set("RedisStringService_key" + i, "RedisStringService_value2");//Redis
}
watch.Stop();
Console.WriteLine("redis 10 万次耗时 "+watch.Elapsed);

watch.Reset();
watch.Start();
for (int i = 0; i < 100000; i++)
{
HttpRuntime.Cache.Insert("RedisStringService_key" + i, "RedisStringService_value2", null, DateTime.Now.AddMinutes(5), TimeSpan.Zero);
}
watch.Stop();
Console.WriteLine("Cache 10 万次耗时 " + watch.Elapsed);