[Samba] sync always, strict sync, cache question

Jeremy Allison jra at samba.org
Wed Sep 17 00:38:13 GMT 2008

On Tue, Sep 16, 2008 at 09:51:33AM -0700, Eric Roseme wrote:

> ---------------------------------------------------------------
> Samba defaults to asynchronous writes.  smbd writes to memory buffer,  
> then returns to processing.  Buffer is flushed to disk later. This is  
> the most efficient behavior.
> Windows CreateFile API has the FILE_FLAG_WRITE_THROUGH flag, which  
> requests synchronous writes.  smbd writes to memory buffer, blocks until  
> buffer contents are written to disk, which results in poor performance,  
> but better data integrity.
> When "strict sync = yes" (default = no) Samba honors the  
> FILE_FLAG_WRITE_THROUGH flag, and results in synchronous writes when  
> called by the CreateFile API.
> When "sync always = yes" (default = no) Samba executes all writes  
> synchronously. This requires that “strict sync = yes”.
> StrictSync  SyncAlways  ff_write_through   Sync-Writes
>     no          no             no                no
>     yes         no             no                no
>     yes         no             yes               Yes (slow)
>     no          yes            yes               no
>     yes         yes            yes/no            yes (very slow)
> Eric Roseme

Great summation Eric, nothing has changed since then so
it's still accurate !



More information about the samba mailing list