Date: Wed, 17 Apr 2002 01:27:27 +0800 From: "Ted Striker" <tedstriker@graffiti.net> To: <scott@avantgo.com>, <freebsd-database@FreeBSD.ORG> Subject: Re: Raid configuration Message-ID: <20020416172727.31988.qmail@graffiti.net>
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I know this was a question regarding Vinum, but, our RAID card only let us set up a RAID10, there was no option to do RAID01. I think that says something about which one is more reliable. ----- Original Message ----- From: Scott Hess <scott@avantgo.com> Date: Tue, 16 Apr 2002 09:40:19 -0700 (PDT) To: FreeBSD DB List <freebsd-database@FreeBSD.ORG> Subject: Re: Raid configuration > So, why'd I draw the diagram if I wasn't going to refer to the disks by > name at any point? If 2 disks fail, there are six possible pairs. > RAID10 stays up if (A|B)&(C|D) stay up (4/6). RAID01 can only stay up if > (A&C)|(B&D) stay up (2/6). > > Sigh, > scott > > On Tue, 16 Apr 2002, Scott Hess wrote: > > Additionally, consider two setups: > > > > RAID10 (stripe of mirror) > > +---------+ > > |+-------+| > > || A = B || > > |+-------+| > > |+-------+| > > || C = D || > > |+-------+| > > +---------+ > > > > RAID01 (mirror of stripes) > > +-----------+ > > |+---+ +---+| > > || A | | B || > > || |=| || > > || C | | D || > > |+---+ +---+| > > +-----------+ > > > > Both have the same uptime for single-disk failures. For two-disk > > failures, RAID10 stays up for 2/3 of the cases, while RAID01 only stays up > > in 1/3 of the cases. > > > > Later, > > scott > > > > > > On Sun, 14 Apr 2002, Chris Dillon wrote: > > > On Sun, 14 Apr 2002, David Drum wrote: > > > > > > > > And when you only have a four-drive configuration, it makes no > > > > > difference which one you use since the chances of a total failure > > > > > is exactly the same either way. Any more drives than that and you > > > > > definately want RAID10. :-) > > > > > > > > The chances of total failure may be the same, but the effort > > > > required to rebuild the RAID is not. If you have 4 9GB disks in a > > > > RAID 0+1 and one goes bad, you have to mirror 18GB once the drive is > > > > replaced. If you have a RAID 1+0, you only have one drive to > > > > mirror, and not a stripe. > > > > > > Ah, yes, I hadn't thought of what it would take to rebuild one. In > > > that case, RAID 0+1 looks like the loser in all situations. > > > > > > -- > > > Chris Dillon - cdillon@wolves.k12.mo.us - cdillon@inter-linc.net > > > FreeBSD: The fastest and most stable server OS on the planet > > > - Available for IA32 (Intel x86) and Alpha architectures > > > - IA64, PowerPC, UltraSPARC, and ARM architectures under development > > > - http://www.freebsd.org > > > > > > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > > with "unsubscribe freebsd-database" in the body of the message > > > > > > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-database" in the body of the message > -- _______________________________________________ Get your free email from http://www.graffiti.net Powered by Outblaze To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-database" in the body of the message
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