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

[Zbigniew Jędrzejewski-Szmek]

On Sat, Mar 21, 2015 at 12:56:51PM +0100, 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.
Let's see what Lennart says. He's travelling currently so this will have to
wait a while.

Zbyszek