Date: Tue, 30 Apr 2002 15:58:09 -0700 (PDT) From: "Andrew P. Lentvorski" <bsder@allcaps.org> To: <utsl@quic.net> Cc: Terry Lambert <tlambert2@mindspring.com>, <freebsd-fs@freebsd.org> Subject: Re: Non-standard root filesystems Message-ID: <20020430141744.P312-100000@mail.allcaps.org> In-Reply-To: <20020430204153.GB3603@quic.net>
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While this sort of mutated into a software RAID discussion, remember that two of the original problems (solid-state media and mounting an unusual FS type) are not RAID-related. utsl@quic.net wrote: > Linux has a syscall (pivot_root) to swap the root with another mounted > filesystem. It is occasionally quite useful, and I've been wondering > about implementing it (or something similar) on FreeBSD. > > Possibly you can tell me why that wouldn't work, or would be a bad > idea. That sounds like a fine idea. What are the issues with doing that? Terry Lambert wrote: > How does Linux handle a half-plex failure detected at boot time? > > It seems to me that the only way to detect this is "not booting", > which means that you're not loading any software capable of > handling the problem, anyway, and you're screwed. > > Hardware RAID doesn't have this problem... But sometimes that's okay. If it can't boot because of failure, the system is still consistent. Things don't have to be automatic, all the time. As long as I can manually reconfigure and boot off of the other plex, I'm okay. I simply want a redundant disk array (RAID 1), effectively. With vinum, I don't have that. A failure on the original boot drives takes the system out--suddenly and badly. However, the failure is *not* in vinum, it's in the way FreeBSD handles mounting /. If the drives weren't redundant, I'd have to do daily backups. My current system is set to shut down gracefully on any disk failure. If need be, I can take a backup image while the system has a failed drive (or is even rebuilding the new one). Given that redundancy, I do monthly backups on my CVS server/bug tracking repository. The amount of work saved over a year given that I am chief/cook/bottle-washer is worth $300 (the price of a 3ware Escalade card). And the line feeding that machine is only a T1; performance isn't an issue. However, I'm now captive to whether 3ware wants to continue supporting their card. That decision is subject to the whim of 3ware management. If the card fails, and 3ware isn't giving out info for supporting their new cards on FreeBSD, I'm toast. It's all a case of balancing price and risk. Terry Lambert wrote: > I guess I don't totally understand the point, other than that > you can use software RAID on / on Linux and not FreeBSD? See my opening statement, the implications reach further than softRAID. > That's not really news, and it's not really an interesting thing to do, > even if it were news. Perhaps. But I would ask about how many people have requested this of vinum before attempting to dismiss it quite so quickly. > It's actually possible to do with hoop-jumping, but it's really > not something I would recommend doing under any circumstances, > anyway. I'd really love to have a pointer to the hoop jumping. It might present some ways around the solid-state media issue as well as helping out with the non-standard fs type. Thanks, -a To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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