ArGest Backup User Guide

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  5. Specifying a Larger (or Smaller) Buffer Size

Specifying a Larger (or Smaller) Buffer Size

BRU operation can sometimes be performed more quickly if a larger buffer is specified, particularly with streaming tape drives. However, on some systems, a smaller buffer size will result in greater speed. The default buffer size, if the -b option is not specified, is read from the brutab file. Normally, this is set to bufsize=32K. If you use a larger buffer, two things happen:

  • 1: Your performance might improve due to larger blocks being read and written in a single action to the archive device.
  • 2: If you are using a tape unit as the archive device, using a larger buffer may allow you to store more data on the tape since the proportion of tape that stores data goes up as the number of inter-record gaps decreases.
  • A smaller buffer size (like 2K or 4K) is often faster when using tape devices that have small buffers or on systems with tape controllers or device drivers that do their own buffering.

    There are several things that can affect the size of the buffer and therefore the tape block size that is written to the archive: