Solaris Tunable Parameters Reference Manual



Controls whether file system metadata syncs will be executed during fsflush invocations. Syncs are done every Nth invocation of fsflush where N= (autoup / tune_t_fsflushr). Because this is an integer division, if tune_t_fsflushr is greater than autoup, a sync will be done on every invocation of fsflush because the code checks to see if its iteration counter is greater than or equal to N. Note that N is computed once on invocation of fsflush. Later changes to tune_t_fsflushr or autoup will have no effect on the frequency of sync operations.

Data Type

Signed integer


1 (enabled)


0 (disabled) or 1 (enabled)


Toggle (on/off)





When to Change

When files are frequently modified over a period of time and the load caused by the flushing perturbs system behavior. Files whose existence, and therefore consistency of state does not matter if the system reboots, are better kept in a TMPFS file system (for example, /tmp). Inode traffic can be reduced on systems running the Solaris 7 and 8 releases by using the mount -noatime option. This option eliminates inode updates when the file is accessed.

A system engaged in realtime processing might want to disable this option and use explicit application file syncing to achieve consistency.

Commitment Level