Re: FFSv1 (UFS1) vs FFSv2 (UFS2)

[tlaronde%polynum.com@localhost]

On Fri, Jul 05, 2019 at 06:10:18AM +0700, Robert Elz wrote:
>     Date:        Wed, 3 Jul 2019 19:43:20 +0200
>     From:        tlaronde%polynum.com@localhost
>     Message-ID:  <20190703174320.GA7939%polynum.com@localhost>
> 
>   | 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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