From: Goffredo Baroncelli <kreij...@inwind.it> Document: - the new parameter CowJournal in journald.conf - the new options --cow-journal and --no-cow-journal for systemd-journal-remote.
Signed-off-by: Goffredo Baroncelli <kreij...@inwind.it> --- man/journald.conf.xml | 56 ++++++++++++++++++++++++++++++++++++++++++ man/systemd-journal-remote.xml | 34 +++++++++++++++++++++++++ 2 files changed, 90 insertions(+) diff --git a/man/journald.conf.xml b/man/journald.conf.xml index 364b58f..9be19b8 100644 --- a/man/journald.conf.xml +++ b/man/journald.conf.xml @@ -362,6 +362,62 @@ <filename>/dev/console</filename>.</para></listitem> </varlistentry> + <varlistentry> + <term><varname>CowJournal=</varname></term> + + <listitem><para>Controls the "no copy on write" attribute for the + journal file. + If <varname>CowJournal=no</varname> this attribute is set. + If <varname>CowJournal=yes</varname> this attribute is reset. + </para> + + <para>For the BTRFS filesystem the "no copy on write" attribute disables + the COW behavior and the checksum feature ; this leads to a faster + journal operations. Instead if this attribute is not set, the COW + behavior and the checksum feature are enabled but the performances are + slower.</para> + + <para>BTRFS uses the checksums to detect a corrupted file; the checksums + are also used to automatically correct the file if a good copy is + available (as in a RAID1 BTRFS filesystems). Without checksums, BTRFS + is not able to detect and to repair a corrupted file.</para> + + <para>In case of a BTRFS filesystem without redundancy (i.e. single + disk), it is safe t<varname>CowJournal=no</varname> because in any case + there is no a good copy available to correct the file.</para> + + <para>Refer to man pages such as + <citerefentry><refentrytitle>btrfs</refentrytitle> + <manvolnum>5</manvolnum></citerefentry> and + <citerefentry><refentrytitle>chattr</refentrytitle> + <manvolnum>1</manvolnum></citerefentry> + for more details.</para> + </listitem> + </varlistentry> + + + + <varlistentry> + <term><varname>CowJournal=</varname></term> + + <listitem><para>Controls the COW/NOCOW attribute for the journal file. + If <varname>CowJournal=no</varname> the journal file has the NOCOW + flags set. + For the BTRFS filesystem this means that the COW behaviour (Copy + On Write) is disable but also the checksum protection is also disabled. + In this case journal operations are faster, but the journal file is not + protected by the filesystem checksums. + If <varname>CowJournal=yes</varname> the journal file has the NOCOW + flag unset, and it is protected by the BTRFS checksum but the + perfomance are slower. + If the the journal file is corrupted on the disk and a good copy + (raid mirror) is available, the checksum are used by BTRFS to rebuild + the file content during a SCRUB process. If the checksum is not + available, the SCRUB process is unable the repair of the journal file. + In case of a single volume filesystem (no RAID), it is safe to have + NoCowJournal=yes.</para></listitem> + </varlistentry> + </variablelist> </refsect1> diff --git a/man/systemd-journal-remote.xml b/man/systemd-journal-remote.xml index 2687662..b14f4e3 100644 --- a/man/systemd-journal-remote.xml +++ b/man/systemd-journal-remote.xml @@ -258,6 +258,40 @@ </varlistentry> <varlistentry> + <term><option>--cow-journal</option></term> + <term><option>--no-cow-journal</option></term> + + <listitem><para>Controls the "no copy on write" attribute for the + journal file. + If <option>--no-cow-journal</option> is passed, this attribute is set. + If <option>--cow-journal</option> is passed, this attribute is reset. + </para> + + <para>For the BTRFS filesystem the "no copy on write" attribute disables + the COW behavior and the checksum feature ; this leads to a faster + journal operations. Instead if this attribute is not set, the COW + behavior and the checksum feature are enabled but the performances are + slower.</para> + + <para>BTRFS uses the checksums to detect a corrupted file; the checksums + are also used to automatically correct the file if a good copy is + available (as in a RAID1 BTRFS filesystems). Without checksums, BTRFS + is not able to detect and to repair a corrupted file.</para> + + <para>In case of a BTRFS filesystem without redundancy (i.e. single + disk), it is safe to pass --no-cow-journal because in any case + there is no a good copy available to correct the file.</para> + + <para>Refer to man pages such as + <citerefentry><refentrytitle>btrfs</refentrytitle> + <manvolnum>5</manvolnum></citerefentry> and + <citerefentry><refentrytitle>chattr</refentrytitle> + <manvolnum>1</manvolnum></citerefentry> + for more details.</para> + </listitem> + </varlistentry> + + <varlistentry> <term><option>--seal</option></term> <term><option>--no-seal</option></term> -- 2.1.0 _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel