Date: Wed, 10 Apr 1996 16:12:36 -0700 From: asami@cs.berkeley.edu (Satoshi Asami) To: DARREND@novell.com Cc: stable@freebsd.org, SCSI@freebsd.org Subject: Re: Disk Mirroring Message-ID: <199604102312.QAA19403@sunrise.cs.berkeley.edu> In-Reply-To: <s16b7c2e.082@fromGW> (DARREND@novell.com)
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* Is there a way to mirror two disks in FreeBSD? The two different * possibilities are at the driver layer or at the filesystem layer. * I imagine the driver layer would be the easiest. Just take the * block to be written and write it out to both disks. The reason I * suggest the filesystem layer is to avoid duplicating the swap space * on both disks. It would be cool if the boot code could * automatically deal with either disk failing and still having the * system boot. Naturally, the driver should be able to deal with * either disk failing. Has anyone given this some thought? With * disks getting real cheap, it is a good way to have some fault * tolerance with out the cost or performance hit of RAID. (Actually, * I think mirroring is one form of RAID.) There is a driver called "ccd" (concatenated disk) that I ported from NetBSD. It is designed primarily for striping disk arrays but it has mirror support so you can use it to mirror partitions by just making it a mirrored 2-disk array. :) Please take a look at http://stampede.cs.berkeley.edu/ccd/ for details. I'm planning to put it into -current soon but there's a 2.1R version too. Satoshi
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