From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: RAID6 Reshape Gone Awry Date: Fri, 03 Aug 2012 06:18:12 -0500 Message-ID: <501BB374.9020607@hardwarefreak.com> References: <8C493F417CC49C6619BBAF45@ryoohko.kodachi.com> Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <8C493F417CC49C6619BBAF45@ryoohko.kodachi.com> Sender: linux-raid-owner@vger.kernel.org To: Flynn Cc: Linux RAID List-Id: linux-raid.ids On 8/3/2012 12:27 AM, Flynn wrote: > My RAID6 is actually a little bit odd in that the drives are split into > 10 partitions. All the partition 5's are a RAID6; all the partition 6's > are a RAID6; etc. md offered the ability, so you _could_ create such a monstrosity. But you never bothered to consider if you _should_ The primary function of RAID is to protect your data in the event of a _disk_ failure. Creating multiple arrays from _partitions_ on the same set of physical disks does nothing to protect one from disk failure. What it can do is cause massive problems for the elevator when you try to reshape 10 arrays simultaneously, which just happen to reside on the same set of disks. By doing this you force the heads on the drives into a massive random seek pattern, bumping all over the platters, top to bottom. This is likely what caused, or is directly related to, your crash. > Suggestions very welcome. Backup what you need to external storage. Blow the entire mess away. Start over from scratch, and build a single RAID6 array, as you should have in the first place. md allows the use of partitions, but not so you can create 50 arrays on the same set of disks, shooting yourself in the foot. Similarly, most cars can travel at velocities over 120 mph, but most people have enough sense not to attempt driving that fast. Learn the difference between "Can I?" and "Should I?". You never bothered to consider the latter when you built this. Please consider it now, for your sake. -- Stan