Copies between local file systems are a daily activity. Files are constantly being moved to locations accessible by systems with different functions and/or storage limits, being backed up and restored, or being moved due to upgraded and/or replaced hardware. Hence, maximizing the performance of copies as well as checksums that ensure the integrity of copies is desirable to minimize the turnaround time of user and administrator activities. Modern parallel file systems provide very high performance for such operations using a variety of techniques such as striping files across multiple disks to increase aggregate I/O bandwidth and spreading disks across multiple servers to increase aggregate interconnect bandwidth.
To achieve peak performance from such systems, it is typically necessary to utilize multiple concurrent readers/writers from multiple systems to overcome various single-system limitations such as number of processors and network bandwidth. The standard cp and md5sum tools of GNU coreutils found on every modern Unix/Linux system, however, utilize a single execution thread on a single CPU core of a single system, hence cannot take full advantage of the increased performance of clustered file systems.
Mutil provides mcp and msum, which are drop-in replacements for cp and md5sum that utilize multiple types of parallelism to achieve maximum copy and checksum performance on clustered file systems. Multi-threading is used to ensure that nodes are kept as busy as possible. Read/write parallelism allows individual operations of a single copy to be overlapped using asynchronous I/O. Multi-node cooperation allows different nodes to take part in the same copy/checksum. Split file processing allows multiple threads to operate concurrently on the same file. Finally, hash trees allow inherently serial checksums to be performed in parallel.