Friday 10 March 2023

File System Performance Metrics

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File system performance is measured by:
  • Latency
    • delay between request and response
    • a measure of the length of time it takes for a single I/O request to be completed from the application's point of view
    • measured separately for read (usually in microseconds) and write (usually in milliseconds) operations
      • If the I/O is a data read, latency is the time it takes for the data to come back. If the I/O is a write, latency is the time for the write acknowledgement to return.
    • affects application's acceleration
  • Throughput / Bandwidth
    • measures how many units of information a system can process in a period of time
    • describes the amount of data able to flow through a point in the data path over a given time
    • throughput and latency are often competing goals - the lower the latency, the higher the throughput
    • measured separately for file system read (usually in GiBps) and file system write (usually in MiBps) operations 
    • typically the best storage metric when measuring data that needs to be streamed rapidly, such as images and video files.
  • Input/Output operations per second (IOPS)
    • number of I/O operations per second
    • measured separately for read and write operations
    • as the number of IOPS requested from the device increases the latency will increase
    • affects application's scalability

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