This is a project aiming to find the average read and write transfer speeds a device is able to achieve by running dd with various block sizes. Currently, block sizes from 512 bytes to 64 MiB are used (512, 1024, 2048, ... 65536, ... 67108864). That's 18 tests. It will help you find the optimal input and output block sizes to use with the respective device to achieve high transfer speeds.
For more detailed info on how to use the script, run:
./dd-bs-benchmark.sh -h
The script needs one of the -r and -w flags, a folder path and optionally, a number.
./dd-bs-benchmark.sh -r /path/to/directory [number]
./dd-bs-benchmark.sh -w /path/to/directory [number]
The flag as well as the folder path are mandatory. The folder path must point to one on the drive to be benchmarked. The last argument, the number is optional and it must be the size in bytes of the temporary file that will be created in the folder. It can only be a natural number a.k.a. positive integer a.k.a. non-negative integer in the form [0-9], like 1234 but not +1234 or -1234 or 12.34 nor 1,234. If no number is provided, 268435456 will be used by default (256 MiB). It should be enough for a slow device, like a memory card or a flash drive, which are relatively slow but if you want to benchmark a faster device, like a Hard Drive or worse, a Solid State Drive you would need to provide a larger file size because 256 MiB would be read or written in less than a second, which will give unreliable results. In read mode (-r), it will create the file just once and read it 18 times. Warning: in write mode (-w), the script will create the file 18 times. Hold that into consideration before benchmarking flash drives, SSDs or other flash memory devices and use files as small as possible.
./dd-bs-benchmark.sh -r /media/user/External_storage 536870912
The command above will create a 512 MiB file with dd containing pseudo-random data in the directory /media/user/External_storage then read it back repeatedly with dd using different block sizes and print the read speeds obtained. If no size were specified, the script would create a file of the default size which is 256 MiB.
./dd-bs-benchmark.sh -w /media/user/External_storage
The command above will create a zeroed-out file with dd using a block size of 512 bytes in the directory /media/user/External_storage and print the write speed obtained then delete the file. It would then create another file using a block size of 1024 bytes, then one with 2 kiB and so on. Because no size was specified, the script will create files of the default size which is 256 MiB.
./dd-bs-benchmark.sh -wt /dev/shm /media/user/External_storage 134217728
By default, with the -w/--write flag, the script will create a file filled with zeroes by reading /dev/zero. If the -t/--temp flag is used, the script will generate a file with random data from /dev/urandom. Reading from /dev/urandom is a CPU-intensive operation and because, apparently, dd uses only 1 CPU, it would not be possible to benchmark a fast device like an SSD or maybe even a hard drive by reading from /dev/urandom because it could not read from it fast enough. A solution would be to read from /dev/urandom and create a file in a temporary directory on a fast drive then copy the file from the fast drive to the drive that needs to be benchmarked. The command above does what the previous one did but the -t flag will create a file with pseudo-random data in /dev/shm, which is a temporary directory stored in the RAM (hence, very fast) on Linux systems then copy it multiple times with different block sizes to /media/user/External_storage.
./dd-bs-benchmark.sh -bwt /dev/shm /dev/sdd 134217728
The command above does what the previous one did but the -b flag tells the script to expect for a path to a block device instead of a directory. It will then write to it, starting with the first sector which means that it will overwrite the partition table and many more other sectors to a total of 134217728 sectors.
This software is licensed under the MIT License (MIT Expat License). The full text can be found in the file LICENSE.