Date: Thu, 22 Feb 2001 15:47:10 -0800 (PST) From: patl@Phoenix.Volant.ORG To: Terry Lambert <tlambert@primenet.com> Cc: freebsd-fs@FreeBSD.ORG Subject: Re: Status of nullfs Message-ID: <ML-3.4.982885630.8528.patl@asimov.phoenix.volant.org> In-Reply-To: <200102222215.PAA26750@usr05.primenet.com>
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On 22-Feb-01 at 14:15, Terry Lambert (tlambert@primenet.com) wrote: > Any mmap'ed writes will fail due to cache coherency problems. If > ... > file are supposed to be treated as identical for both. Thanks, Terry. Given your clear and concise explanation, I don't think that nullfs will be suitable for my use. > There are a number of patches to manually enforce coherency; as > far as I know, they don't deal with the pager path, and, since > the coherency is explicit, the /usr vs. /null_usr problem is > not resolved. Check the list archives to obtain the patches. > > If you need stacking for a project, FiST has been ported to > FreeBSD. Personally, I have not used it, but supposedly it > addresses the vm_object_t aliasing caused coherency problems. Hmm. That looks like it might be a possibility; I'll look into it a bit deeper. Of course I might be on completely the wrong tack. I'm looking into methods to reduce the disk overhead and maintainance issues with setting up jailed virtual hosts. The hosts generally won't have any user shell access; but will run some combination of SMTP, IMAP, POP, FTP, HTTP, etc. services. It seems like it should be possible to set up a prototype jail directory tree with all of the necessary software installed. That directory should be shared read-only with all jails; with each jail having a read-write filesystem layered on top with the necessary per-virtual-host configuration and data files. It would be even better if there were two per-jail layers, one underneath with config files, read-only, and the one on top for data files read-write. But a single per-jail layer would be OK. Ideally, root on the host machine should have read-write access to both the shared prototype and the 'raw' overlayed directories. (By 'raw', I mean only what is actually in the overlayed tree, without the prototype underneath.) The raw access isn't really necessary; but it would make a few things easier. I'll be happy to hear of any suggestions on how to do this on 4-STABLE; or any reasonable alternative schemes to accomplish the same goal. Thanks, -Pat To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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