Date: Tue, 13 Feb 2007 18:16:31 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-fs@FreeBSD.ORG, chris@sigd.net Subject: Re: UFS2 with SAN Message-ID: <200702131716.l1DHGVsN000719@lurza.secnetix.de> In-Reply-To: <6FC9F9894A9F8C49A722CF9F2132FC2204C9DAB6@ms05.mailstreet2003.net>
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Chris Haulmark wrote: > If your responses on this SAN thread would not be productive, please > stay out. I am not interested to hear lectures about what is impossible. But maybe others are interested to hear that information. > I asked about if anyone has tried to use UFS2 with only one node to > have write/read only while the rest would be read only. And you already got the answer, see Eric's mail. He wrote: | This will result it the read/write system seeing the data ok, | and the rest getting corrupt data without knowing it, and | probably crashing. UFS2 is not cluster aware. Eric is right. For UFS to be cluster-aware, it would need to implement a cache-coherency protocol, so every node knows what data is up-to-date and what data is stale. UFS doesn't do that at all because it was designed as a local-only file system. The only way it would work is to mount _all_ of the nodes read-only. When you need to update data, you must remount the file system read-write on one node _and_ unmount it on all other nodes. I don't think that you want to do that, though. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart Any opinions expressed in this message are personal to the author and may not necessarily reflect the opinions of secnetix GmbH & Co KG in any way. FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "UNIX was not designed to stop you from doing stupid things, because that would also stop you from doing clever things." -- Doug Gwyn
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