CYCBUFF.CONF(5) InterNetNews Documentation CYCBUFF.CONF(5)NAMEcycbuff.conf - Configuration file for INN CNFS storage method
DESCRIPTION
This file defines the cyclical buffers that make up the storage pools
for CNFS (Cyclic News File System). Some options controlling the
behavior of the CNFS storage system can also be set here. cycbuff.conf
is required if the CNFS (Cyclic News File System) storage method is
used. INN will look for it in pathetc (as set in inn.conf).
CNFS stores articles in logical objects called metacycbuffs. Each
metacycbuff is in turn composed of one or more physical buffers called
cycbuffs. As articles are written to the metacycbuff, each article is
written to the next cycbuff in the list in a round-robin fashion
(unless "sequential" mode is specified, in which case each cycbuff is
filled before moving on to the next). This is so that you can
distribute the individual cycbuffs across multiple physical disks and
balance the load between them. Note that in order to use any cycbuff
larger than 2 GB, you need to build INN with the --enable-largefiles
option.
For information about how to configure INN to use CNFS, see
storage.conf(5).
Blank lines and lines beginning with a hash sign ("#") are ignored.
All other lines must be of one of the following forms:
cycbuffupdate:<interval>
refreshinterval:<interval>
cycbuff:<name>:<file>:<size>
metacycbuff:<name>:<buffer>[,<buffer>,...][:<mode>]
(where items enclosed in [] are optional). Order is mostly not
significant, but all cycbuff lines must occur before all metacycbuff
lines. Long lines can be continued on the next line by ending the line
with a backslash ("\").
cycbuffupdate:<interval>
Sets the number of articles written before the cycbuff header is
written back to disk to <interval>. Under most operating systems,
the header doesn't have to be written to disk for the updated data
to be available to other processes on the same system that are
reading articles out of CNFS, but any accesses to the CNFS cycbuffs
over NFS will only see the data present at the last write of the
header. After a system crash, all updates since the last write of
the CNFS header may be lost. The default value, if this line is
omitted, is 25, meaning that the header is written to disk after
every 25 articles stored in that cycbuff.
refreshinterval:<interval>
Sets the interval (in seconds) between re-reads of the cycbuff
header to <interval>. This primarily affects nnrpd and controls
the frequency with which it updates its knowledge of the current
contents of the CNFS cycbuffs. The default value, if this line is
omitted, is 30.
cycbuff:<name>:<file>:<size>
Configures a particular CNFS cycbuff. <name> is a symbolic name
for the buffer, to be used later in a metacycbuff line. It must be
no longer than seven characters. <file> is the full path to the
buffer file or block device, and must be no longer than 63
characters. <size> is the length of the buffer in kilobytes (1 KB
is 1024 bytes). If <file> is not a block device, it should be
<size> * 1024 bytes long.
If you're trying to stay under 2 GB, keep your sizes below 2097152.
metacycbuff:<name>:<buffer>[,<buffer>,...][:<mode>]
Specifies a collection of CNFS buffers that make up a single
logical storage location from the perspective of INN. Metacycbuffs
are referred to in storage.conf as storage locations for articles,
so in order to actually put articles in a cycbuff, it has to be
listed as part of some metacycbuff which is then referenced in
storage.conf.
<name> is the symbolic name of the metacycbuff, referred to in the
options: field of "cnfs" entries in storage.conf. It must be no
longer than eight characters. <buffer> is the name of a cycbuff
(the <name> part of a cycbuff line), and any number of cycbuffs may
be specified, separated by commas.
If there is more than one cycbuff in a metacycbuff, there are two
ways that INN can distribute articles between the cycbuffs. The
default mode, "INTERLEAVE", stores the articles in each cycbuff in
a round-robin fashion, one article per cycbuff in the order listed.
If the cycbuffs are of wildly different sizes, this can cause some
of them to roll over much faster than others, and it may not give
the best performance depending on your disk layout. The other
storage mode, "SEQUENTIAL", instead writes to each cycbuff in turn
until that cycbuff is full and then moves on to the next one,
returning to the first and starting a new cycle when the last one
is full. To specify a mode rather than leaving it at the default,
add a colon and the mode ("INTERLEAVE" or "SEQUENTIAL") at the end
of the metacycbuff line.
innd only reads cycbuff.conf on startup, so if you change anything in
this file and want innd to pick up the changes, you have to use
"ctlinnd xexec innd"; "ctlinnd reload all ''" is not sufficient.
When articles are stored, the cycbuff into which they're stored is
saved as part of the article token. In order for INN to retrieve
articles from a cycbuff, that cycbuff must be listed in cycbuff.conf.
However, if INN should not write to a cycbuff, it doesn't need to be
(and shouldn't be) listed in a metacycbuff.
This provides an easy way to retire a cycbuff. Just remove it from its
metacycbuff, leaving in the cycbuff line, and restart innd (with, for
example, "ctlinnd xexec innd"). No new articles will be put into the
cycbuff, but neither will any articles expire from it. After you no
longer need the articles in the cycbuff, just remove it entirely from
cycbuff.conf. Then all of the articles will appear to have been
deleted to INN, and the next nightly expire run will clean up any
remaining references to them.
Adding a new cycbuff just requires creating it (see below), adding a
cycbuff line, adding it to a metacycbuff, and then restarting innd.
CREATING CYCBUFFS
When creating a new cycbuff, there are two different methods for
creating the buffers in which the articles will be stored.
1. Create a large file on top of a regular file system. The easiest
way to do this is probably with dd(1), using a command like:
dd if=/dev/zero of=/path/to/cycbuff bs=1024 count=<size>
where <size> is the size from the cycbuff line in cycbuff.conf.
INSTALL contains a script that will generate these commands for you
from your cycbuff.conf file.
This is the simplest method, but has the disadvantage that very
large files on regular file systems can be fairly slow to access,
particularly at the end of the file, and INN incurs unnecessary
file system overhead when accessing the cycbuff.
2. Use block devices directly. If your operating system allows you to
call mmap() on block devices (Solaris and recent versions of Linux
do, FreeBSD at last report does not), this is the recommended
method since you can avoid all of the native file system overhead.
Note that some OSes do not support files larger than 2 GB, which
will limit the size you can make a single cycbuff, but you can
still combine many cycbuffs into each metacycbuff. Very old
versions of Linux (before 2.4 kernels, that raised the limit to
2 TB) are known to have this limitation; FreeBSD does not. Some
OSes that support large files don't support direct access to block
devices for large partitions (Solaris prior to Solaris 7, or not
running in 64-bit mode, is in this category); on those OSes, if you
want cycbuffs over 2 GB, you'll have to use regular files. If in
doubt, keep your cycbuffs smaller than 2 GB.
Partition the disk to make each partition equal to or smaller than
2 GB. If you're using Solaris, set up your partitions to avoid the
first cylinder of the disk (or otherwise the cycbuff header will
overwrite the disk partition table and render the cycbuffs
inaccessible). Then, create device files for each block device
you're going to use.
It's not recommended to use the block device files in /dev, since
the news system doesn't have permission to write to them and
changing the permissions of the system device files may affect
something else. Instead, use mknod(1) to create a new set of block
devices (in somewhere like pathspool/cycbuffs that's only writable
by the news user). To do this, run "ls -Ll" on the devices in /dev
that correspond to the block devices that you want to use. The
major and minor device numbers are in the fifth and sixth columns
(right before the date), respectively. Then run mknod like:
mknod <file> b <major> <minor>
where <file> is the path to the device to create (matching the
<file> part of the cycbuff line) and <major> and <minor> are the
major and minor device numbers as discovered above.
Here's a short script to do this when given the path to the system
device file as an argument:
#!/bin/sh
base=`echo "$1" | sed 's%.*/%%'`
major=`ls -Ll "$1" | awk '{print $5}' | tr -d ,`
minor=`ls -Ll "$1" | awk '{print $6}`
mkdir -p <pathspool in inn.conf>/cycbuffs
mknod <pathspool>/cycbuffs/"$base" b "$major" "$minor"
chown news:news <pathspool>/cycbuffs/"$base"
chmod 644 <pathspool>/cycbuffs/"$base"
Make sure that the created files are owned by the news user and
news group, as specified at configure time (the default being
"news" for both). Also make sure that the permissions on the
devices allow the news user to read and write, and if you want
other users on the system to be able to use sm to retrieve
articles, make sure they're world-readable.
Once you have everything configured properly and you start innd, you
should see messages in news.notice that look like:
innd: CNFS-sm No magic cookie found for cycbuff ONE, initializing
where "ONE" will be whatever you called your cycbuff.
HISTORY
Written by Katsuhiro Kondou <kondou@nec.co.jp> for InterNetNews.
Rewritten into POD by Russ Allbery <rra@stanford.edu>.
$Id: cycbuff.conf.pod 8987 2010-02-16 19:48:45Z iulius $
SEE ALSOctlinnd(8), innd(8), nnrpd(8), sm(1), storage.conf(5).
INN 2.5.3 2010-02-16 CYCBUFF.CONF(5)
