Date: Tue, 16 Apr 2002 09:40:19 -0700 (PDT) From: Scott Hess <scott@avantgo.com> To: FreeBSD DB List <freebsd-database@FreeBSD.ORG> Subject: Re: Raid configuration Message-ID: <Pine.LNX.4.44.0204160935420.6159-100000@river.avantgo.com> In-Reply-To: <Pine.LNX.4.44.0204160908060.5530-100000@river.avantgo.com>
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.LNX.4.44.0204160935420.6159-100000>