Test ResultsĪfter the benchmark ran through, we got the following results. A NVMe was used as the storage for the files tested. CPU was a Intel i9-9000k with logical 16 Cores and 32 GB of RAM. NETCore 3.1.2 on Windows 10 Pro Version 1 Build 19041. All data read until the offset is cached, which should make access to any random access with a smaller offset much faster. The DataReader is a custom class that allocates a buffer of the size of the file but only reads to the currently used max offset. Open the file in a FileStream and create a BinaryReader from that, than read random integers Open the file in a FileStream and create a BinaryReader from that, than read random bytes Open the file in a FileStream and create a BufferedStream with an initial size of the file size from that, than read random integers Open the file in a FileStream and create a BufferedStream with an initial size of the file size from that, than read random bytes Open the file in a FileStream and create a BufferedStream from that, than read random integers Open the file in a FileStream and create a BufferedStream from that, than read random bytes Open the file in a custom DataReader and read random integers Open the file in a custom DataReader and read random bytes

Open the file as a FileStream and read random integers Open the file as a FileStream and read random bytes Read the whole file into a byte array and read random integers

Read the whole file into a byte array and read random bytes For the random access read, we are reading a byte and an integer to test if there is a difference in the performance due to the amount of data read. For each of these files 1 000 random reads are tested. With the help of the amazing BenchmarkDotnet I’ve wrote a test suite to gather performance insights into different methods for random access on files. This works pretty well for small files (few MB) but if the files get larger, the performance hit due to the initial read of the whole file gets significant. Since a few years I’m running a project where I read a file into a byte buffer and do a lot of random accesses on it.

Random zero byte file