From owner-freebsd-hackers@FreeBSD.ORG  Thu Sep 16 18:03:02 2004
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id F0F0A16A4CE
	for <freebsd-hackers@freebsd.org>;
	Thu, 16 Sep 2004 18:03:02 +0000 (GMT)
Received: from athena.softcardsystems.com (mail.softcardsystems.com
	[12.34.136.114])
	by mx1.FreeBSD.org (Postfix) with ESMTP id AC23043D2F
	for <freebsd-hackers@freebsd.org>;
	Thu, 16 Sep 2004 18:03:02 +0000 (GMT)
	(envelope-from sah@softcardsystems.com)
Received: from athena (athena [12.34.136.114])i8GJ2c74029881;
	Thu, 16 Sep 2004 14:02:38 -0500
Date: Thu, 16 Sep 2004 14:02:38 -0500 (EST)
From: Sam <sah@softcardsystems.com>
X-X-Sender: sah@athena
To: Gary Corcoran <garycor@comcast.net>
In-Reply-To: <4149D73C.5030309@comcast.net>
Message-ID: <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>
	<4149D73C.5030309@comcast.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
cc: freebsd-hackers@freebsd.org
Subject: Re: ZFS
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 16 Sep 2004 18:03:03 -0000

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.

Sam