From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vyacheslav Dubeyko Subject: Re: Does nilfs2 do any in-place writes? Date: Wed, 15 Jan 2014 16:01:44 +0400 Message-ID: <1389787304.3913.28.camel@slavad-ubuntu> References: <1389783139.3913.23.camel@slavad-ubuntu> Reply-To: slava-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=dubeyko.com; s=default; h=Mime-Version:Content-Transfer-Encoding:Content-Type:References:In-Reply-To:Date:Cc:To:Reply-To:From:Subject:Message-ID; bh=yP+ataptiM3rLxH2TfT3YeC0QfoCjeaPAPDqP9gQbFg=; b=mWJmVQaQqNCvEP9ldERX2VS3IXRl7W9knttjYbwrFfJrQyYNOmdNJZ31jWpyPEXMa2l98AwsLGtko80Q/ZVGs/NIGTbjD8uqSkohyFdFebCgqQhMoJqDHASbNRhFPvQZ; In-Reply-To: Sender: linux-nilfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Clemens Eisserer Cc: linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Hi Clemens, On Wed, 2014-01-15 at 12:44 +0100, Clemens Eisserer wrote: > Hi Vyacheslav, > > > The main approach of NILFS2 is COW (copy-on-write) policy. It means that > > all data and metadata are written in log manner. Only superblocks are > > placed in fixed positions and updated there. First superblock is located > > in the volume begin, second one in the volume end. > > Can you give me an estime how often the superblock is updated / written to? > NILFS2 has special method nilfs_sb_need_update() [1] and special constant NILFS_SB_FREQ [2] that it is used usually for definition frequency of superblocks updating. So, as far as I can judge, default value of such frequency under high I/O load is 10 seconds (Minimum interval of periodical update of superblocks (in seconds)). With the best regards, Vyacheslav Dubeyko. [1] http://lxr.free-electrons.com/source/fs/nilfs2/the_nilfs.h#L254 [2] http://lxr.free-electrons.com/source/fs/nilfs2/the_nilfs.h#L252 -- To unsubscribe from this list: send the line "unsubscribe linux-nilfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html