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

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Date:	Tue, 01 Aug 2006 23:52:06 -0400
From:	David Masover <ninja@...phack.com>
To:	Ian Stirling <ian.stirling@...ve.plus.com>
CC:	David Lang <dlang@...italinsight.com>,
	Nate Diller <nate.diller@...il.com>,
	Adrian Ulrich <reiser4@...nkenlights.ch>,
	"Horst H. von Brand" <vonbrand@....utfsm.cl>, ipso@...ppymail.ca,
	reiser@...esys.com, lkml@...productions.com, jeff@...zik.org,
	tytso@....edu, linux-kernel@...r.kernel.org,
	reiserfs-list@...esys.com
Subject: Re: Solaris ZFS on Linux [Was: Re: the " 'official' point of  view"expressed
 by kernelnewbies.org regarding reiser4 inclusion]

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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