bionic (8) vfs_aio_linux.8.gz

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.