7 Replies Latest reply: Mar 21, 2007 9:43 AM by 74513 RSS

    FILESYSTEMIO_OPTIONS=setall always safe?

    74513
      Hi,
      I'm quite confused with the parameter FILESYSTEMIO_OPTIONS.

      I need to know if setting the FILESYSTEMIO_OPTIONS=setall is ALWAYS working correctly regardless of the type of used storage?

      Is there any situation where setting FILESYSTEMIO_OPTIONS=setall may fail or may leave the database in some inconsistency upon disk crash?

      Thanks
        • 1. Re: FILESYSTEMIO_OPTIONS=setall always safe?
          cd_2
          On which platform?

          C.
          • 2. Re: FILESYSTEMIO_OPTIONS=setall always safe?
            74513
            Solaris.

            Thanks
            • 3. Re: FILESYSTEMIO_OPTIONS=setall always safe?
              cd_2
              I suppose you have to wait for someone with Solaris knowhow then. Or you could use this forum's search function, maybe there's been a discussion on this topic already.

              C.
              • 4. Re: FILESYSTEMIO_OPTIONS=setall always safe?
                546494
                hi,

                libaio: async I/O library for database data and log writes. Oracle performs writes in batches or lists, which are submitted to the operating system using the listio() functionality. The listio() asynchronous I/O facility was added specifically to optimize database performance.

                you should enable the parameter FILESYSTEMIO_OPTIONS=setall for system performance.

                rgds

                alan.
                • 5. Re: FILESYSTEMIO_OPTIONS=setall always safe?
                  74513
                  Sorry but that's not clear.

                  1- FILESYSTEMIO_OPTIONS=setall means, Oracle will try to do async and direct io if possible. But what about when the underlying storage and system can't provide the functionality? Oracle is in error?

                  2- Being in ASYNC mode is really safe? what about a disk crash. Oracle has received an acknowledgement when writing to disk but the async write may be lost during a crash disk.

                  3- Regarding the directio now:
                  Do I have to set forcedirectio on the filesystem level even if I set FILESYSTEMIO_OPTIONS=setall (or, the setall implicitly let Oracle do the forcedirectio even if the parameter was not set on the vfstab side)?

                  Thanks
                  • 6. Re: FILESYSTEMIO_OPTIONS=setall always safe?
                    293720
                    Sorry but that's not clear.

                    1- FILESYSTEMIO_OPTIONS=setall means, Oracle will
                    try to do async and direct io if possible. But what
                    about when the underlying storage and system can't
                    provide the functionality? Oracle is in error?
                    If you have setall, and Oracle can't do kernelized asynchronous I/O, it will fall back to threaded async I/O, which could be severely detrimental to performance. So, on Solaris, you want to switch it on, but only if you're sure that your I/O subsystem and complete I/O path support it!
                    2- Being in ASYNC mode is really safe? what about a
                    disk crash. Oracle has received an acknowledgement
                    when writing to disk but the async write may be lost
                    during a crash disk.
                    No, async I/O means that Oracle queues up a bunch of writes and waits for the O/S signal that they are complete. In the case of LGWR, it will continue waiting on log file sync, until it gets a signal from the O/S that the write is complete. AIO is long proven technology in Oracle, and does not suffer from any such weakness.

                    >
                    3- Regarding the directio now:
                    Do I have to set forcedirectio on the filesystem
                    level even if I set FILESYSTEMIO_OPTIONS=setall (or,
                    the setall implicitly let Oracle do the forcedirectio
                    even if the parameter was not set on the vfstab
                    side)?
                    Not sure on this one....we're on Solaris, but use raw everywhere, so mount option is not an issue for us. What FS? UFS? VxFS?

                    -Mark
                    • 7. Re: FILESYSTEMIO_OPTIONS=setall always safe?
                      74513
                      Thanks Mark for the details.

                      Regarding point 3 (forcedirectio), it's really hard to get the real picture about it.
                      I will do some tests to validate this point.

                      Thanks,
                      Vincent