Re: what is our answer to ZFS?

From: Pavel Machek (pavel_at_ucw.cz)
Date: 11/22/05

  • Next message: Steven Rostedt: "Re: test time-warps [was: Re: 2.6.14-rt13]" 
    Date:	Tue, 22 Nov 2005 01:45:31 +0100
To: Rob Landley <rob@landley.net>

    Hi!

    > > If It happenned, Sun or someone has port it to linux.
    > > We will need some VFS changes to handle 128 bit FS as "Jörn ENGEL"
    > > mentionned previous mail in this thread. Is there any plan or action
    > > to make VFS handle 128 bit File Sytems like ZFS or future 128 bit
    > > File Systems ? Any VFS people reply to this, please?
    >
    > I believe that on 64 bit platforms, Linux has a 64 bit clean VFS. Python says
    > 2**64 is 18446744073709551616, and that's roughly:
    > 18,446,744,073,709,551,616 bytes
    > 18,446,744,073,709 megs
    > 18,446,744,073 gigs
    > 18,446,744 terabytes
    > 18,446 ... what are those, petabytes?
    > 18 Really big lumps of data we won't be using for a while yet.
    >
    > And that's just 64 bits. Keep in mind it took us around fifty years to burn
    > through the _first_ thirty two (which makes sense, since Moore's Law says we
    > need 1 more bit every 18 months). We may go through it faster than we went
    > through the first 32 bits, but it'll last us a couple decades at least.
    >
    > Now I'm not saying we won't exhaust 64 bits eventually. Back to chemistry, it
    > takes 6.02*10^23 protons to weigh 1 gram, and that's just about 2^79, so it's
    > feasible that someday we might be able to store more than 64 bits of data per
    > gram, let alone in big room-sized clusters. But it's not going to be for
    > years and years, and that's a design problem for Sun.
    >
    > Sun is proposing it can predict what storage layout will be efficient for as
    > yet unheard of quantities of data, with unknown access patterns, at least a
    > couple decades from now. It's also proposing that data compression and
    > checksumming are the filesystem's job. Hands up anybody who spots
    > conflicting trends here already? Who thinks the 128 bit requirement came
    > from marketing rather than the engineers?

    Actually, if you are storing information in single protons, I'd say
    you _need_ checksumming :-).

    [I actually agree with Sun here, not trusting disk is good idea. At
    least you know kernel panic/oops/etc can't be caused by bit corruption on
    the disk.]

                                                                    Pavel 

    -- 
Thanks, Sharp!
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