Login or Register to Ask a Question and Join Our Community

Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

vfs_aio_linux(8) [centos man page]

VFS_AIO_LINUX(8)					    System Administration tools 					  VFS_AIO_LINUX(8)

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.

Samba 4.0							    06/17/2014							  VFS_AIO_LINUX(8)

Check Out this Related Man Page

VFS_READAHEAD(8)					    System Administration tools 					  VFS_READAHEAD(8)

NAME

       vfs_readahead - pre-load the kernel buffer cache

SYNOPSIS

       vfs objects = readahead

DESCRIPTION

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

       This vfs_readahead VFS module detects read requests at multiples of a given offset (hex 0x80000 by default) and then tells the kernel via
       either the readahead system call (on Linux) or the posix_fadvise system call to pre-fetch this data into the buffer cache.

       This module is useful for Windows Vista clients reading data using the Windows Explorer program, which asynchronously does multiple file
       read requests at offset boundaries of 0x80000 bytes.

       The offset multiple used is given by the readahead:offset option, which defaults to 0x80000.

       The size of the disk read operations performed by vfs_readahead is determined by the readahead:length option. By default this is set to the
       same value as the readahead:offset option and if not set explicitly will use the current value of readahead:offset.

       This module is stackable.

OPTIONS

       readahead:offset = BYTES
	   The offset multiple that causes readahead to be requested of the kernel buffer cache.

       readahead:length = BYTES
	   The number of bytes requested to be read into the kernel buffer cache on each readahead call.

       The following suffixes may be applied to BYTES:

       o   K - BYTES is a number of kilobytes

       o   M - BYTES is a number of megabytes

       o   G - BYTES is a number of gigabytes

EXAMPLES

		[hypothetical]
		vfs objects = readahead

VERSION

       This man page is correct for version 3.0.25 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.

Samba 4.0							    06/17/2014							  VFS_READAHEAD(8)
Man Page