On Fri, Jul 05, 2019 at 06:10:18AM +0700, Robert Elz wrote:
> Date: Wed, 3 Jul 2019 19:43:20 +0200
> From: tlaro...@polynum.com
> Message-ID: <20190703174320.ga7...@polynum.com>
>
> | But if somebody had numbers about tests comparing FFSv1 and FFSv2 and
> | the efficiency (for formatting,
>
> FFSv1 pre-allocates (ie: zeroes) all of the inode blocks that will ever
> be inode blocks. FFSv2 doesn't, it keeps track of which inode blocks
> have been initialised, and clears new ones when they're actually needed
> (if one is needed, it will be being written to, to store some new inode
> data, so aside from the cost of zeroing a block of mem, this is more or
> less free - atually cheaper than FFSv1 as there is no need or point in
> reading the existing inode block ... but it doesn't happen often so the
> operational difference is negligible).
>
> Since an empty FFS filesystem is essentially just super block and backups,
> cylinder group headers, and inode blocks, not init'ing the inode blocks
> (which are the vast majority of what a FFSv1 init needs to write) saves
> lots of newfs time.
>
Thank you for the explanation.
Best,
--
Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
http://www.kergis.com/
http://www.sbfa.fr/
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