Re: [9fans] venti and "contrib": RFC

[erik quanstrom <quanstro@quanstro.net>]

On Thu Jan  5 16:24:58 EST 2012, yarikos@gmail.com wrote:
> 2012/1/5 Bakul Shah <bakul@bitblocks.com>:
> > You'd save a bunch of energy if you only powered up venti
> > disks once @ 4AM for a few minutes (and on demand when you
> > look at /n/dump).  Though venti might have fits! And the disks
> > might too! So may be this calls for a two level venti? First
> > to an SSD RAID and a much less frequent venti/copy to hard
> > disks.
> 
> I think you're confusing kenfs+worm with fossil+venti in sense that
> ken fs is a complete cache for worm while fossil is a write cache for
> venti. You need venti running all the time.

this only could work if you assume that everything in the worm
is also in the cache, and you've configured your cache to cache the worm.
since these days the cache is often similar in performance to the worm, the
default we use is to not copy the worm into the cache.  this would just
result in more i/o.

so tl;dr you need the worm available at all times be it venti+fossil
or ken fs/cwfs

- erik