lkml.org 
[lkml]   [2006]   [Aug]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Solaris ZFS on Linux [Was: Re: the " 'official' point of view"expressed by kernelnewbies.org regarding reiser4 inclusion]
    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.

    And if you've got to spin the drive up, you've just added another
    order of magnitude.

    You can see why a flash backup of the write cache may be nicer.
    You can do it if the disk isn't spinning.
    It uses moderately less energy - and at a much lower rate, which
    means the power supply can be _much_ cheaper. I'd guess it's the
    difference between under $2 and $10.
    And if you can use it as a lazy write cache for laptops - things
    just got better battery life wise too.
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2006-08-02 01:55    [W:0.030 / U:61.584 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site