From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Upgrading a software RAID Date: Sat, 30 May 2009 14:32:08 -0400 Message-ID: <4A217BA8.1080208@tmr.com> References: <4A1EA095.9090406@usherbrooke.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4A1EA095.9090406@usherbrooke.ca> Sender: linux-raid-owner@vger.kernel.org To: Maxime Boissonneault Cc: robin@robinhill.me.uk, linux-raid@vger.kernel.org List-Id: linux-raid.ids Maxime Boissonneault wrote: > > Robin Hill a =E9crit : >> On Mon May 25, 2009 at 01:05:15PM -0400, Maxime Boissonneault wrote: >> >> =20 >>> Hello, >>> I am using Ubuntu Hardy with 3x500GB drives and the following RAID >>> configuration : >>> >>> /boot is on a 100MB RAID1 >>> / is on a 30GB RAID0 >>> /home is on a 906GB RAID5 >>> >>> =20 >> Ouch - why RAID0 for /? If you lose a single drive then all the >> configuration, etc. is down the drain. I'd suggest rethinking this >> while you're going through the rebuild process anyway. >> >> =20 > That is why I do backups of / on /home regularily. I first did a RAID= 0=20 > for performance. I did some testing on performance of RAID0,1,5 and=20 > RAID1 was pretty lousy (I put the results of my tests here :=20 > http://cqed.physique.usherbrooke.ca/~mboisson/htpc.php?sec=3Draid_tes= t ) > I guess I should have used a RAID5, but RAID1 seems like a terrible=20 > idea considering the really bad performances. > >>> I want to replace the 3 drives by 3 1TB drives. >>> >>> Here is how I planned to do it : >>> 0- Backup my /home on some external disk. >>> 1- backup / with something like : >>> sudo tar cvpzf /backup.tgz --exclude=3D/media --exclude=3D/proc >>> --exclude=3D/lost+found --exclude=3D/backup.tgz --exclude=3D/mnt=20 >>> --exclude=3D/sys >>> --exclude=3D/home / >>> mv /backup.tgz $1 >>> =20 >> You'll need to do the tar in single user mode (init 1) to ensure the= re's >> no open files when you're backing up (or use a bootable CD). >> >> =20 > I used this backup before to restore the system and it seemed to work= =20 > pretty well. >>> 2- Replace 1 disk >>> 3- Boot and let the RAID1 and RAID5 reconstruct >>> =20 >> You'll have to boot to a CD then - your root FS is trashed at this >> point. >> >> =20 >>> 4- Replace 1 other disk >>> 5- Boot and let the RAID1 and RAID5 reconstruct again >>> 6- Replace the last disk >>> 7- Boot and let the RAID1 and RAID5 reconstruct one last time >>> 8- Boot and restore the backup on the RAID0 / partition. >>> 9- Resize the /home partition to 1 TB. >>> >>> I suspect there will be a problem replacing the primary disk, but I= =20 >>> guessed >>> that I could solve this simply by changing which is the primary dis= k=20 >>> in the >>> BIOS. >>> >>> Is there any other problem that will or could happen ? >>> >>> =20 >> See above - your current plan is pretty much doomed I'm afraid. >> >> =20 >>> For example, I am not sure if the raid manager is on the /boot=20 >>> partition or >>> on the /. I guess if it is on /, it won't work at all since the rai= d=20 >>> manager >>> itself won't be able to run ? >>> Also, is it possible to boot and access a command line to restore=20 >>> the backup >>> with a failed / partition ? >>> >>> I am also unsure about how I should proceed to resize the /home=20 >>> partition. >>> Is this done through mdadm ? >>> >>> =20 >> No, you'll have to delete & recreate the partition using fdisk. >> >> =20 >>> Please enlight me on any problems that I will have. >>> >>> =20 >> >> An easier option (assuming you want to keep the arrays as currently >> setup) would be to boot from a CD and do a full copy of each of the >> 500GB disks to the 1TB disks. You'll then just need to resize the >> last partition (assuming /home is set up on the last partition on th= e >> disks anyway) and grow the array and filesystem. >> >> A _better_ option (if possible) would be to install all the drives i= n >> the system concurrently, then you can boot from CD and create arrays= on >> the new drives and copy the data across. You'll also need to update >> mdadm.conf (and the initrd if you're using one) to indicate the new >> array IDs. >> >> HTH, >> Robin >> =20 > > I can not install more drives in the computer. It is a home theater=20 > computer in a small case. I was expecting to be able to let the raid=20 > manage the copies itself. > > If the / was on a RAID5, would it be able to boot with 2 disks ? > If so, is it possible to convert my RAID0 to a RAID5 ? > For example, I could boot on a CD, backup / onto /home, delete the=20 > RAID0 array and recreate it as RAID5, then restore the backup. Would=20 > this work ? Based on my testing (somewhat old now) and regular use, I would say=20 raid10 is probably your best bet. It's fast and secure, and with the -f= 2=20 option for "far" copies it's able to give high transfer rates. --=20 bill davidsen CTO TMR Associates, Inc "You are disgraced professional losers. And by the way, give us our mon= ey back." - Representative Earl Pomeroy, Democrat of North Dakota on the A.I.G. executives who were paid bonuses after a federal bailout= =2E -- 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