[systemd-devel] [PATCH] Set the NOCOW flag for the journal via tmpfiles

Goffredo Baroncelli kreijack at libero.it
Sun Mar 29 12:43:45 PDT 2015

did you find the time to give a look a these patches ? Do you have any suggestions ?


On 2015-03-21 12:56, Goffredo Baroncelli wrote:
> Hi all,
> these patches set reverts the commit 11689d2 "journald: turn off COW for
> journal files on btrfs" which enables *unconditionally* the NOCOW flag for the
> journal files. The reason was that the performances of the journal file format
> are very bad on btrfs, and decrease during the time. Disabling the COW
> behavior, the perfomances increase.
> Unfortunately disabling the COW behavior leads to disable the BTRFS checksums,
> which in turn prevents BTRFS to rebuild a corrupted file in a RAID
> filesystem [3].
> To avoid that I proposed a patch which introduces a configurable option to
> disables the "turn off COW" behavior[1]. Lennart commented that instead he
> prefer to set the NOCOW attribute via tmpfile.d snippets.
> A further patches set was proposed and accepted [2] to extend systemd-tmpfiles
> to change the file attributes.
> This last patches set removes the "turn off COW" behavior (patch #1) and
> introduces a new tmpfiles.d snippet which enable the NOCOW beahvior for the
> journal files (patch #2). So a sysadmin can disable this setting overriding
> this file configuration.
> BR
> G.Baroncelli
> [1] Re: [systemd-devel] [RFC][PATCH] Add option to enable COW for journal file
> https://www.mail-archive.com/systemd-devel@lists.freedesktop.org/msg28724.html
> [2] https://www.mail-archive.com/systemd-devel@lists.freedesktop.org/msg29313.html
> [3] http://en.wikipedia.org/wiki/Btrfs#Checksum_tree_and_scrubbing
> --
> gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
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gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
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