Date: Sun, 5 Dec 1999 00:45:12 +0100 (CET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: mckusick@flamingo.McKusick.COM (Kirk McKusick) Cc: msmith@FreeBSD.ORG, match@elen.utah.edu, current@FreeBSD.ORG Subject: Re: Mounting one FS on more than one system Message-ID: <199912042345.AAA30805@yedi.iaf.nl> In-Reply-To: <199912042044.MAA05073@flamingo.McKusick.COM> from Kirk McKusick at "Dec 4, 1999 12:44:43 pm"
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As Kirk McKusick wrote ... > Mounting on more than one system is generally problematical unless > you are willing to have all systems read-only. The problem is cache > coherence between the machines. If one changes a block, the other > machines will not see it. Basically, this is why we have the NFS > filesystem. That lets a disk be mounted on one machine, but shared > out to others. If you wanted to write a protocol that would allow > for multiple machines, then you would need to have some central > coordinator running some sort of coherency protocol with a complexity > akin to that of NFS. I wonder how Tru64 is doing it. IIRC V5.0 Tru64 can do a cluster filesystem. A CFS must have solved the coherency issue in some way. Older revs had distributed raw devices (for Oracle and the like) but that had all I/O go through one cluster member that did all the I/O for that DRD. The I/O from the other cluster members was done via the Memory Channel to the DRD-serving machine. Interesting.. Wilko -- | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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