1VFS_AIO_LINUX(8)          System Administration tools         VFS_AIO_LINUX(8)
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NAME

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

10       vfs objects = aio_linux
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DESCRIPTION

13       This VFS module is part of the samba(7) suite.
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15       The aio_linux VFS module enables asynchronous I/O for Samba on Linux
16       kernels that have the kernel AIO calls available without using the
17       Posix AIO interface. Posix AIO can suffer from severe limitations. For
18       example, on some Linux versions the real-time signals that it uses are
19       broken under heavy load. Other systems only allow AIO when special
20       kernel modules are loaded or only allow a certain system-wide amount of
21       async requests being scheduled. Systems based on glibc (most Linux
22       systems) only allow a single outstanding request per file descriptor
23       which essentially makes Posix AIO useless on systems using the glibc
24       implementation.
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26       To work around all these limitations, the aio_linux module was written.
27       It uses the Linux kernel AIO interface instead of the internal Posix
28       AIO interface to allow read and write calls to be processed
29       asynchronously. A queue size of 128 events is used by default. To
30       change this limit set the "aio num events" parameter below.
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32       Note that the smb.conf parameters aio read size and aio write size must
33       also be set appropriately for this module to be active.
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35       This module MUST be listed last in any module stack as the Samba VFS
36       pread/pwrite interface is not thread-safe. This module makes direct
37       pread and pwrite system calls and does NOT call the Samba VFS pread and
38       pwrite interfaces.
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EXAMPLES

41       Straight forward use:
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43                   [cooldata]
44                path = /data/ice
45                aio read size = 1024
46                aio write size = 1024
47                vfs objects = aio_linux
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OPTIONS

50       aio_linux:aio num events = INTEGER
51           Set the maximum size of the event queue that is used to limit
52           outstanding IO requests.
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54           By default this is set to 128.
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VERSION

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

60       The original Samba software and related utilities were created by
61       Andrew Tridgell. Samba is now developed by the Samba Team as an Open
62       Source project similar to the way the Linux kernel is developed.
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66Samba 4.2                         06/19/2018                  VFS_AIO_LINUX(8)
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