Date: Sat, 1 Aug 1998 11:11:36 +0930 From: Greg Lehey <grog@lemis.com> To: "Daniel T. Hagan" <dhagan@vt.edu>, questions@FreeBSD.ORG Subject: Re: Disk mirroring with ccd Message-ID: <19980801111136.P11960@freebie.lemis.com> In-Reply-To: <Pine.OSF.3.96.980731152549.9938A-100000@rottweiler.cslab.vt.edu>; from Daniel T. Hagan on Fri, Jul 31, 1998 at 03:34:37PM -0400 References: <Pine.OSF.3.96.980731152549.9938A-100000@rottweiler.cslab.vt.edu>
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On Friday, 31 July 1998 at 15:34:37 -0400, Daniel T. Hagan wrote: >> From the man page for ccd(8): > > Disk Mirroring > You can configure the ccd to ``mirror'' any even number of disks. > See ccdconfig(8) for how to specify the necessary flags. In an event of a > disk failure, you can use dd(1) to recover the failed disk. Note that a > one-disk ccd is not the same as the original partition. In particular, > this means if you have a filesystem on a two-disk mirrored ccd and one of > the disks fail, you cannot mount and use the remaining partition as > itself; you have to configure it as a one-disk ccd. > > Just to be sure I understand what this is saying, if I have: > > ccd0 ?? CCDF_MIRROR /dev/sd1e /dev/sd2e > > as the configuration, and sd1 fails, can I change the configuration to: > > ccd0 ?? none /dev/sd2e > > And recover the data from ccd0? Correct. > As an added question, how does interleaving affect disk mirroring under > ccd? It spreads the data more evenly, thus balancing the load on the disks. In combination with mirroring, you need at least 4 disks. > Any recommended values? 256 kB. It should be large enough that most requests just go to one stripe, and small enough to balance the access well. You might like to check out Vinum, a replacement for ccd. http://www.lemis.com/vinum.html. Greg -- See complete headers for address and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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