From owner-freebsd-current Sat Dec 4 14: 5:20 1999 Delivered-To: freebsd-current@freebsd.org Received: from critter.freebsd.dk (critter.freebsd.dk [212.242.40.131]) by hub.freebsd.org (Postfix) with ESMTP id E983614C2E; Sat, 4 Dec 1999 14:05:07 -0800 (PST) (envelope-from phk@critter.freebsd.dk) Received: from critter.freebsd.dk (localhost [127.0.0.1]) by critter.freebsd.dk (8.9.3/8.9.2) with ESMTP id XAA14996; Sat, 4 Dec 1999 23:05:02 +0100 (CET) (envelope-from phk@critter.freebsd.dk) To: Mike Smith Cc: match@elen.utah.edu, current@FreeBSD.ORG, mckusick@mckusick.com Subject: Re: Mounting one FS on more than one system In-reply-to: Your message of "Sat, 04 Dec 1999 13:53:26 PST." <199912042153.NAA04820@mass.cdrom.com> Date: Sat, 04 Dec 1999 23:05:02 +0100 Message-ID: <14994.944345102@critter.freebsd.dk> From: Poul-Henning Kamp Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message <199912042153.NAA04820@mass.cdrom.com>, Mike Smith writes: >The sticking issue that we discussed was allowing more than one system to >mount a given filesystem; I pressume we're talking R/W mounts here, since a R/O mount obviously would not be a problem. With UFS/FFS there are significant meta-data caching which would need not only high-level locking (for atomic rename(2) calls) but also low-level locking (who allocates a particular free block). In short: a major hazzle. It might be possible to allow one machine R/W and have the others R/O snoop on the same device, but a more agressive write policy would be needed to get closer to real-time behaviour. -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message