svn commit: r199744 - stable/8/share/man/man4
mav at FreeBSD.org
Tue Nov 24 09:13:16 UTC 2009
Date: Tue Nov 24 09:13:15 2009
New Revision: 199744
Add ada(4) man page.
- copied unchanged from r199532, head/share/man/man4/ada.4
stable/8/share/man/man4/ (props changed)
--- stable/8/share/man/man4/Makefile Tue Nov 24 09:10:43 2009 (r199743)
+++ stable/8/share/man/man4/Makefile Tue Nov 24 09:13:15 2009 (r199744)
@@ -15,6 +15,7 @@ MAN= aac.4 \
+ ada.4 \
Copied: stable/8/share/man/man4/ada.4 (from r199532, head/share/man/man4/ada.4)
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ stable/8/share/man/man4/ada.4 Tue Nov 24 09:13:15 2009 (r199744, copy of r199532, head/share/man/man4/ada.4)
@@ -0,0 +1,138 @@
+.\" Copyright (c) 2009 Alexander Motin <mav at FreeBSD.org>
+.\" All rights reserved.
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.Dd November 19, 2009
+.Dt ADA 4
+.Nd ATA Direct Access device driver
+.Cd device ada
+driver provides support for direct access devices, implementing
+command protocol, that are attached to the system through a host adapter
+supported by CAM subsystem.
+Host adapter must also be separately configured into the system before a
+direct access device can be configured.
+.Sh COMMAND QUEUING
+Command queueing allows the device to process multiple transactions
+concurrently, often re-ordering them to reduce the number and length of
+defines two types of queueing:
+.Tn TCQ (Tagged Command Queueing, PATA legacy)
+.Tn NCQ (Native Command Queueing, SATA).
+device driver takes full advantage of the NCQ, when supported.
+To ensure that transactions to distant portions of the media,
+which may be deferred indefinitely by servicing requests nearer the current
+head position, are completed in a timely fashion, an ordered
+transaction is sent every 7 seconds during continuous device operation.
+.Sh CACHE EFFECTS
+Many direct access devices are equipped with read and/or write caches.
+Parameters affecting the device's cache are reported in device IDENTIFY data
+and can be examined and modified via the
+.Xr camcontrol 8
+The read cache is used to store data from device-initiated read ahead
+operations as well as frequently used data.
+The read cache is transparent
+to the user and can be enabled without any adverse effect.
+with a read cache come from the factory with it enabled.
+The write cache can greatly decrease the latency of write operations
+and allows the device to reorganize writes to increase efficiency and
+This performance gain comes at a price.
+Should the device
+lose power while its cache contains uncommitted write operations, these
+writes will be lost.
+The effect of a loss of write transactions on
+a file system is non-deterministic and can cause corruption.
+devices age write transactions to limit vulnerability to a few transactions
+recently reported as complete, but it is none-the-less recommended that
+systems with write cache enabled devices reside on an Uninterruptible
+Power Supply (UPS).
+device driver ensures that the cache and media are synchronized upon
+final close of the device or an unexpected shutdown (panic) event.
+This ensures that it is safe to disconnect power once the operating system
+has reported that it has halted.
+.Sh SYSCTL VARIABLES
+The following variables are available as both
+.Xr sysctl 8
+.Xr loader 8
+.Bl -tag -width 12
+This variable determines how many times the
+driver will retry a READ or WRITE command.
+This does not affect the number of retries used during probe time or for
+driver dump routine.
+This value currently defaults to 4.
+This variable determines how long the
+driver will wait before timing out an outstanding command.
+The units for this value are seconds, and the default is currently 30
+.Bl -tag -width ".Pa /dev/ada*" -compact
+.It Pa /dev/ada*
+ATA device nodes
+.Sh SEE ALSO
+.Xr ahci 4 ,
+.Xr siis 4 ,
+.Xr ad 4
+.Xr da 4
+driver first appeared in
+.Fx 8.0 .
+.An Alexander Motin Aq mav at FreeBSD.org .
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