From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: migrating from RAID5 to RAID10 Date: Fri, 18 Jun 2010 12:39:10 +1000 Message-ID: <20100618123910.711b527b@notabene.brown> References: <20100609151132.GA10082@libra.CS.Berkeley.EDU> <20100611005231.401529c0@natsu> <20100610195851.GA8408@libra.CS.Berkeley.EDU> <4C18F39E.8010600@tmr.com> <20100617072631.09641f48@notabene.brown> <20100617174445.GB8450@libra.CS.Berkeley.EDU> <20100617224657.GD8450@libra.CS.Berkeley.EDU> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100617224657.GD8450@libra.CS.Berkeley.EDU> Sender: linux-raid-owner@vger.kernel.org To: Gilad Arnold Cc: Bill Davidsen , Roman Mamedov , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, 17 Jun 2010 15:46:57 -0700 Gilad Arnold wrote: > On Thu, Jun 17, 2010 at 10:44:45AM -0700, Gilad Arnold wrote: > > This leads me to think that even with 2 drives, RAID10/f2 is a better > > choice than RAID1. Is this a fair assessment? > > Okay, I found the benchmarks that support this hypothesis ;-) > > > And, if it is the case, can RAID5 be converted to RAID10/f2 > > on-the-fly, or would I have to take the longer path? (i.e. degrade > > RAID5, start RAID10 in degraded mode, copy data, kill RAID5 and > > rebuild RAID10) > > Some more reading leads me to think that on-the-fly RAID5 to RAID10/f2 > conversion wouldn't work. However, I'm tempted to believe that I can > avoid the data copy phase entirely and skip straight to RAID10 rebuild: > > 1. Shutdown the RAID5. > > 2. Create a RAID10/f2 on top of one drive + missing, ignoring mdadm's > warnings about an existing array. If I'm not terribly wrong, this > will give me a degraded RAID10 that still has all my data in place. I cannot imagine why you would think that all your data would be in place. I can assure that it would not. NeilBrown > > 3. Add the second drive to the RAID10 and watch it rebuild. > > > Apologies for my petty questions ;-) Advice appreciated. > > Gilad