Re: [Samba] sync always, strict sync, cache question
On Wed, Sep 17, 2008 at 2:38 AM, Jeremy Allison [EMAIL PROTECTED] wrote: 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 nono yes no nono yes no yes Yes (slow) no yesyes no yes yesyes/noyes (very slow) Eric Roseme Great summation Eric, nothing has changed since then so it's still accurate ! Thanks, Jeremy. Thank you both for the professional reply. Unfortunately, you have confirmed my suspicions. :) I think I'll head back to NFS and give it another try. They too on the list are very helpful. Viva GNU! Chris. -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/listinfo/samba
Re: [Samba] sync always, strict sync, cache question
Chris Fanning wrote: snip But I am worried about the cache that Samba makes use of. We would like samba to write to disk immediately. We've found these two options for smb.conf sync always = yes strict sync = yes I can't quiet see the difference between the two in my case. If I set 'sync always = yes' _or_ 'strict sync = yes', I can copy files at 70MB/s (similar to NFS using async). If I set both options, file transfer speed drops to about 20MB/s Does that mean that I do need to set both options to ensure the cache is written to disk before the server returns the ok to the client? How could I test this? And now while I'm here ;) , does anyone have any other recommendations for this kind of setup? Thanks, Chris. Hi Chris, I did an investigation on this in 2003. Here are the results. Not sure if things have changed since then. --- 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 nono yes no nono yes no yes Yes (slow) no yesyes no yes yesyes/noyes (very slow) Eric Roseme -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/listinfo/samba
Re: [Samba] sync always, strict sync, cache question
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 nono yes no nono yes no yes Yes (slow) no yesyes no yes yesyes/noyes (very slow) Eric Roseme Great summation Eric, nothing has changed since then so it's still accurate ! Thanks, Jeremy. -- To unsubscribe from this list go to the following URL and read the instructions: https://lists.samba.org/mailman/listinfo/samba
