From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brown Subject: Re: Best strategy to incrementally replace smaller HDDs Date: Fri, 09 Sep 2011 14:34:46 +0200 Message-ID: References: <1315565285.2291.25.camel@michal-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1315565285.2291.25.camel@michal-laptop> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 09/09/2011 12:48, Micha=C5=82 Sawicz wrote: > Hi all, given the configuration below: > * 8 x 1TB HDDs > * 2 x 2TB HDDs > > On which I currently have: > * (10 x 1TB) RAID6 - persistent storage > * (2 x 1TB) system / temporary storage etc. > By this do you mean that you have 8 x 1TB drives with a 1 TB partition=20 on each, and 2 x 2T drives with 2 x 1TB partition on each? So that the= =20 two big disks are shared with both raids? > I want to replace the 1TB drives for 2TB ones on an as-needed basis, > what strategy would you recommend? This sounds like you are thinking that you can replace a single disk in= =20 your RAID6 array and get more storage - changing 10 x 1 TB raid6 =3D 8T= B=20 into 9 x 1TB + 1 x 2TB raid6 =3D 9 TB. It doesn't work like that. You= =20 will have to replace /all/ your 1 TB devices with 2 TB devices (and mov= e=20 the second raid off the two existing 2TB devices) - all members of the=20 raid6 must be the same size. To help you plan your upgrades, it is also useful to know your=20 partitioning scheme (for example, do you use LVM?), whether you have th= e=20 space to put lots more drives in the system or must do it one drive at = a=20 time, whether you can take the system off-line during the process, and=20 whether you need to do the upgrade quickly or can spend a week or so at= =20 it (some of these are conflicting requirements). Before you think about upgrading, however, make sure you have a solid=20 backup. Then make sure you have a backup of that backup - and a plan=20 for how to restore everything if something goes horribly wrong. > > 1. If I moved to 2TB RAID6 members (using RAID0 on the 1TB driv= es), > I would need to replace two of the drives just to match curr= ent > capacity. Each next 2TB drive would get me 1TB additional > capacity (but actually I'd need to replace two to gain > anything). That sounds to be most future-proof, but most > expensive. > 2. If I moved to 2TB RAID5 members, that would reduce redundanc= y > but replacing just two would gain me 2TB capacity. Most of t= he > above still applies. > 3. If I kept to 1TB RAID6 (two on the 2TB drives), I would redu= ce > the redundancy to just one drive if it was the 2TB drive tha= t > failed, but each new drive would gain me 1TB capacity and I = only > need to replace one-by-one. This sounds like the cheapest, b= ut > worst possible approach. > > So, am I missing something? What do you think? -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html