From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adam Goryachev Subject: Re: Use RAID-6! Date: Wed, 17 Apr 2013 14:45:14 +1000 Message-ID: <516E28DA.7070102@websitemanagers.com.au> References: <15345091.8.1366130671716.JavaMail.root@zimbra> <516DABF2.5050409@tigertech.com> <516DAF21.5040409@aei.mpg.de> <516DD433.50100@tigertech.com> <516DEAD4.7080305@bucksch.org> <516DFC4F.5000908@websitemanagers.com.au> <516E24C8.9080803@tigertech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <516E24C8.9080803@tigertech.com> Sender: linux-raid-owner@vger.kernel.org To: Robert L Mathews Cc: Linux RAID List-Id: linux-raid.ids On 17/04/13 14:27, Robert L Mathews wrote: > But complete disk death doesn't seem to be the normal failure mode. If > the failure is spurious, as so many seem to be, and temporarily > affects an array so that each disk has a different event count, that > isn't a disaster under RAID 1. If worst comes to worst, you can pick > one disk to use and pretend RAID doesn't even exist. You don't need to > get the members to successfully sync into an array to read the data. > But if each disk in a RAID 5 or RAID 6 array gets a different event > count, or if the disks refuse to easily assemble into an active array > for any other reason, all your data is inaccessible until you fix the > RAID problem. I avidly read the details of every RAID 5 [and 6] > disaster on the list, and almost every one would be trivially easy to > fix under RAID 1, with no risk of complete data loss. It's heartbreaking. RAID1 of course fails the requirement of a single filesystem that requires more space than a single disk can provide. Of course, you can then consider LVM2, multiple mount points, or RAID10 or RAID1 + linear etc.... but most people still prefer to see a single block device. Dealing with multiple RAID1 and a linear could lead to more complex issues as well. In any case, as mentioned previously, the majority of issues are caused by mis-configuration, if we could add some configuration verification to mdadm or similar, then we might be able to warn more people prior to things failing. Regards, Adam -- Adam Goryachev Website Managers www.websitemanagers.com.au