From owner-freebsd-hackers Thu Oct 28 18:56:10 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id 7D35B14EAE for ; Thu, 28 Oct 1999 18:56:00 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id SAA14208; Thu, 28 Oct 1999 18:55:53 -0700 (PDT) (envelope-from dillon) Date: Thu, 28 Oct 1999 18:55:53 -0700 (PDT) From: Matthew Dillon Message-Id: <199910290155.SAA14208@apollo.backplane.com> To: Zhihui Zhang Cc: "Chris D. Faulhaber" , Michael Beckmann , hackers@FreeBSD.ORG Subject: Re: Limitations in FreeBSD References: Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :> :> The document is not quite right. The maximum size is limited to :> 8 Terrabytes due to block-size conversions done in the kernel which are :> independant of the filesystem block size. : :Can you tell me how to get the 8TB value? I know all the things about :indirect blocks and I know that we use negative numbers for those indirect :blocks. Thanks. : :-Zhihui The kernel uses 512 byte blocks internally. 32 bit block number quantities are used. To avoid sign problems we only allow 31 bits to be used within the kernel (negative block number quantities are also used within the kernel to identify meta-data). So: 2^31 = 2 billion x 512 = 1 TB. Hmm. That isn't 8 TB. I think we might have a problem over 1 TB with mmap() and the VM system. Grr. Maybe the I/O subsystem too. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message