From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ross Vandegrift Subject: Re: RAID-6 support in kernel? Date: Mon, 3 Jun 2002 15:53:24 -0400 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20020603195324.GA11678@willow.seitz.com> References: <1023125615.1051.1283.camel@peecee> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1023125615.1051.1283.camel@peecee> To: Gregory Leblanc Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids > > It'll waste 9 drives, giving me a total capacity of 7n instead of 14n. > > And, by definition, RAID-6 _can_ withstand _any_ two-drive failure. > > This is certainly not true. > > Combining N RAID-5 into a stripe wastes on N disks. > > 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 the > machine itself. This could become a lot less of an issue. I recall Neil Brown recently mentioning that he was thinking about journalling RAID code. This would do away with long resyncs much like journalling filesystems did away with long fscks. Obviously, I'm not sure if it's something he'll decide to do or not, but it would really increase the viability of hot spares. Ross Vandegrift ross@willow.seitz.com