NAME

       vfs_aio_linux - implement async I/O in Samba vfs using Linux kernel aio calls

SYNOPSIS

       vfs objects = aio_linux

DESCRIPTION

       This VFS module is part of the samba(7) suite.

       The aio_linux VFS module enables asynchronous I/O for Samba on Linux kernels that have the
       kernel AIO calls available without using the Posix AIO interface. Posix AIO can suffer
       from severe limitations. For example, on some Linux versions the real-time signals that it
       uses are broken under heavy load. Other systems only allow AIO when special kernel modules
       are loaded or only allow a certain system-wide amount of async requests being scheduled.
       Systems based on glibc (most Linux systems) only allow a single outstanding request per
       file descriptor which essentially makes Posix AIO useless on systems using the glibc
       implementation.

       To work around all these limitations, the aio_linux module was written. It uses the Linux
       kernel AIO interface instead of the internal Posix AIO interface to allow read and write
       calls to be processed asynchronously. A queue size of 128 events is used by default. To
       change this limit set the "aio num events" parameter below.

       Note that the smb.conf parameters aio read size and aio write size must also be set
       appropriately for this module to be active.

       This module MUST be listed last in any module stack as the Samba VFS pread/pwrite
       interface is not thread-safe. This module makes direct pread and pwrite system calls and
       does NOT call the Samba VFS pread and pwrite interfaces.

EXAMPLES

       Straight forward use:

                   [cooldata]
                path = /data/ice
                aio read size = 1024
                aio write size = 1024
                vfs objects = aio_linux

OPTIONS

       aio_linux:aio num events = INTEGER
           Set the maximum size of the event queue that is used to limit outstanding IO requests.

           By default this is set to 128.

VERSION

       This man page is correct for version 4.0 of the Samba suite.

AUTHOR

       The original Samba software and related utilities were created by Andrew Tridgell. Samba
       is now developed by the Samba Team as an Open Source project similar to the way the Linux
       kernel is developed.