Setting the Write Throttle

The -o wr_throttle=n option limits the number of outstanding write kilobytes for one file to n. By default, Sun QFS file systems set the wr_throttle to 16 megabytes.

If a file has n write kilobytes outstanding, the system suspends an application that attempts to write to that file until enough bytes have completed the I/O so that the application to be resumed.

If your site has thousands of streams, such as thousands of NFS-shared workstations accessing the file system, you can tune the -o wr_throttle=n option in order to avoid flushing excessive amounts of memory to disk at once. Generally, the number of streams multiplied by 1024 x the n argument to the -o wr_throttle=n option should be less than the total size of the host system's memory minus the memory needs of the Oracle Solaris OS, as shown in this formula:

number-of-streams x n x 1024 < total-memory - Solaris-OS-memory-needs

For turnkey applications, you might want to use a size larger than the default 16,384 kilobytes to keep more pages in memory.