Re: Solaris ZFS on Linux [Was: Re: the " 'official' point of view"expressed by kernelnewbies.org regarding reiser4 inclusion]

[David Masover <ninja@slaphack.com>]

Ian Stirling wrote:
> David Masover wrote:
> > David Lang wrote:
> >
> > > On Mon, 31 Jul 2006, David Masover wrote:
> > >
> > > > Oh, I'm curious -- do hard drives ever carry enough 
> > > > battery/capacitance to cover their caches?  It doesn't seem like it 
> > > > would be that hard/expensive, and if it is done that way, then I 
> > > > think it's valid to leave them on.  You could just say that other 
> > > > filesystems aren't taking as much advantage of newer drive features 
> > > > as Reiser :P
> > >
> > >
> > > there are no drives that have the ability to flush their cache after 
> > > they loose power.
> >
> >
> > Aha, so back to the usual argument:  UPS!  It takes a fraction of a 
> > second to flush that cache.
>
> You probably don't actually want to flush the cache - but to write
> to a journal.
> 16M of cache - split into 32000 writes to single sectors spread over
> the disk could well take several minutes to write. Slapping it onto
> a journal would take well under .2 seconds.
> That's a non-trivial amount of storage though - 3J or so, 40mF@12V -
> a moderately large/expensive capacitor.

Before we get ahead of ourselves, remember:  ~$200 buys you a huge 
amount of battery storage.  We're talking several minutes for several 
boxes, at the very least -- more like 10 minutes.

But yes, a journal or a software suspend.
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