From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?iso-8859-1?Q?Jakob_=D8stergaard?= Subject: Re: RAID-6 support in kernel? Date: Tue, 4 Jun 2002 22:20:53 +0200 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20020604222053.C31741@unthought.net> References: <1023125615.1051.1283.camel@peecee> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <1023125615.1051.1283.camel@peecee>; from gleblanc@linuxweasel.com on Mon, Jun 03, 2002 at 10:33:24AM -0700 To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Mon, Jun 03, 2002 at 10:33:24AM -0700, Gregory Leblanc wrote: > On Mon, 2002-06-03 at 02:25, Derek Vadala wrote: > On Mon, 3 Jun 2002, Roy Sigurd Karlsbakk wrote: > =20 > > It'll waste 9 drives, giving me a total capacity of 7n inst= ead of 14n.=20 > > And, by definition, RAID-6 _can_ withstand _any_ two-drive = failure. > =20 > This is certainly not true.=20 > =20 > Combining N RAID-5 into a stripe wastes on N disks.=20 >=20 > Hot spares are quite a nice way to increase the reliability of your > arrays, somewhat. You can still be in trouble if a second disk fails > before the resync finishes, but at that point you're probably talking > about something of a more catastrophic failure, perhaps outside of th= e > machine itself. =20 What often happens (in my experience) is, that a number of disks build = up bad blocks. One day, you hit one of those bad blocks, and that one disk is= kicked from the array. When you re-sync, you *will* hit the remaining bad blocks on the other = disks, causing the array to fail completely. Using hot-spares will "automate" this failure - meaning that an adminis= trator may not be anywhere near the system when this total failure happens. Not using hot-spares is less "automatic" in the lucky case where everyt= hing works, but it also assures that an administrator actually is near the s= ystem when the total failure is likely to occur. --=20 =2E............................................................... : jakob@unthought.net : And I see the elder races, : :.........................: putrid forms of man : : Jakob =D8stergaard : See him rise and claim the earth, : : OZ9ABN : his downfall is at hand. : :.........................:............{Konkhra}...............: - To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html