From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: RAID-6 support in kernel? Date: Tue, 4 Jun 2002 14:50:39 -0400 (EDT) Sender: linux-raid-owner@vger.kernel.org Message-ID: References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: To: Derek Vadala Cc: Linux Kernel Mailing List , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sun, 2 Jun 2002, Derek Vadala wrote: > You can always fake this effect by combining two 8-disk RAID-5s into a > RAID-0. It's not technically RAID-6, but can withstand a 2-disk failure, > although not _any_ 2-disk failure. However, it's my understanding that > RAID-6 cannot withstand _any_ two disk failure either (see the above > thread). I think (hope) you meant 1+5, which will stand any three disk failure, and up to 1+N/2 if just the right drives fail. They never do, of course. > I also suspect that the use of dual RAID-5s combined with the CPU overhead > of ATA will kill most systems under any kind of load. For that matter, the > 2x parity hit from RAID-6 probably wouldn't make you CPU too happy either, > even if there was a kernel driver that implemented it. I doubt it. Unless you run a system with heavy CPU demand there are lots of cycles for this stuff. I run 0+1 several places and I don't see serious CPU load. I would be very interested in RAID-6 in the kernel, but I have the feeling that RAID-6 means diferent things to diferent people, judging from posts here and articles online. I haven't found the performance info you, I assume I will. -- bill davidsen CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.