Date: Sat, 29 Nov 1997 00:51:07 -0500 From: Jerry Hicks <jerry_hicks@bigfoot.com> To: hackers@freebsd.org Subject: Re: Drive Mirroring Message-ID: <347FAD4B.D1E682A@bigfoot.com> References: <Pine.BSF.3.96.971128105430.219A-100000@trojanhorse.ml.org>
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Jamil J. Weatherbee wrote: > > I have two exact duplicate drives and I want the second (sd1) to be an > exact duplicate of the first. Unfortunately ccd doesn't work here because > the drives aren't bootable, you cannot install on ccd drives from the cds > etc. One way to accomplish this is to go to single-user, sync, and then > dd if=/dev/sd0 of=/dev/sd1 bs=1024k. Unfortunately using this method on a > running system probably will corrupt the hell out of the copied over > filesystem. I've also tried using dump, but for these 4.3 giggers it > takes about 2 hours every night to remake filesystems on the second drive > and dump | restore to it. Can anyone think of a way I could maintain an > entire mirrored system without ccd, perhaps some software that nightly > looks at the changes on one drive and puts them over to the second without > basically rewriting the whole thing. Using QNX, we developed a cellular switch which boots from a flash 'disk'. A ram disk is created and the root filesystem is created there. The contents of the root filesystem are extracted from a gzipped archive on the flash before entering userland. An unused byte of the memory in the CMOS clock chip is used to save a persistent status code indicating whether to boot in operational, faulted, or service modes. You can get flash for a PC in several forms, including PCMCIA adapters for widely available flash cards. We used ZiaTech hardware which features user-writable flash integrated on the CPU board. IMO, this sort of configuration would be pretty neat to have for a FreeBSD net server. It alleviates a lot of the concerns one might deploying a high-availability system. Software upgrades are a snap too. We do ours remotely (worldwide from Memphis, TN). I don't specifically know how to work out the FreeBSD swapping related issues. Don't think it would be much though (?) Off to www.dejanews.com... Good Luck, Jerry Hicks jerry_hicks@bigfoot.com
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