Date: Thu, 16 Sep 2004 14:30:39 -0400 From: Gary Corcoran <garycor@comcast.net> To: Sam <sah@softcardsystems.com> Cc: freebsd-hackers@freebsd.org Subject: Re: ZFS Message-ID: <4149DBCF.8010908@comcast.net> In-Reply-To: <Pine.LNX.4.60.0409161401110.28550@athena> References: <41483C97.2030303@fer.hr> <Pine.LNX.4.60.0409151047230.21034@athena> <Pine.GSO.4.61.0409161010020.29724@mail.ilrt.bris.ac.uk> <Pine.GSO.4.61.0409161528520.29724@mail.ilrt.bris.ac.uk> <Pine.LNX.4.60.0409161040480.28550@athena> <4149D73C.5030309@comcast.net> <Pine.LNX.4.60.0409161401110.28550@athena>
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Sam wrote: > On Thu, 16 Sep 2004, Gary Corcoran wrote: > >> Sam wrote: >> >>> On Thu, 16 Sep 2004, Jan Grant wrote: >>> >>>> On Thu, 16 Sep 2004, Sam wrote: >>>> >>>>> Let's suppose you generate an exabyte of storage per year. Filling >>>>> a 64-bit >>>>> filesystem would take you approximately 8 million years. >>>> >>>> >>>> >>>> Hang on, I'm not sure I know where these numbers are coming from. >>>> >>>> 1PB is - what? 2^50 bytes? That looks closer to 2^64 than your >>>> figures indicate. I'd imagine an exabyte a year ought to be topping out >>>> after 16 years. I'm missing about half-a-dozen orders of magnitude >>>> somewhere it seems. >>> >>> >>> >>> 1PB is indeed 2^50 bytes, but filesystems don't address on the byte, >>> but on the block (1K, 4K, 8k, ...). The numbers I'm using assume >>> the filesystem addresses on the sector, which is unrealistically >>> small. Jack it up to a 16K blocksize and you jump a few hundred >>> ZB in size. >> >> >> You have to be able to *seek* on a byte boundary. Hence doesn't a >> "64-bit" filesystem indeed mean "only" 2^64 bytes? > > > Only for the file you're seeking on. Yeah, okay, there's multiple definitions of what "64-bit filesystem" is referring to. So what are FreeBSD's current filesystem limitations? 2^64 bytes files, and 2^64 blocks per filesystem? But I seem to recall some problems as people were approaching a terabyte or two ??? Gary
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