Date: 06 Oct 2005 13:18:47 -0400 From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> To: "Chad Leigh -- Shire.Net LLC" <chad@shire.net> Cc: freebsd-questions@freebsd.org Subject: Re: md device backing files on nfs mounts? Message-ID: <44ek6yzhqg.fsf@be-well.ilk.org> In-Reply-To: <380986F7-B6AA-4F66-88FE-722D45E1AC80@shire.net> References: <67F3ED9B-5977-41E1-BABE-F4F17399EAF6@shire.net> <44oe62zizr.fsf@be-well.ilk.org> <380986F7-B6AA-4F66-88FE-722D45E1AC80@shire.net>
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"Chad Leigh -- Shire.Net LLC" <chad@shire.net> writes: > On Oct 6, 2005, at 10:51 AM, Lowell Gilbert wrote: > > > "Chad Leigh -- Shire.Net LLC" <chad@shire.net> writes: > > > > > >> Can the files that back an md device be resident on an nfs mount? > >> > >> I run some jails with each having its own root based on an md > >> device. > >> I am thinking of having a backend nfs server have all the storage > >> and > >> serve it to various front end servers. If one front end server went > >> down I could easily bring it up on another one. Kind of poor-man's > >> redundancy > >> > > > > How do you get the NFS mount before you have a root? > > Just the jails would be on md devices on the nfs mounted filesystem. > Ie, main computer boots normally, mounts nfs filesystem, then mounts > md devices backed by files on the nfs fielsystem Yes, okay, that seems obvious now. Maybe I need more caffeine. I just tried it without the jails and was able to mount and use the filesystem. The permissions *are* a little tricky, because root is (as usual) mapped to nobody on my NFS mounts, and needs write access on the backing file. I did the procedure from the last example in the mdconfig(8) manual, and it worked just like on a local disk. There might have been some anomalies with the output of ls(1), but I can't reproduce those now. You might want to try measuring performance if you implement this; it could have some strange interactions with VM and buffering. Clever idea, by the way. > > Chad > > > Also, I suspect the permissions might be a little tricky... > > > > Some kind of netbooting might work. -- Lowell Gilbert, embedded/networking software engineer, Boston area http://be-well.ilk.org/~lowell/
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