I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
Matt
You will have to reinstall because if you add two more 500GB drives to make your set up into a three drive horse, you then need to format each drive and synchronise them together creating the new logical RAID volume so no data can be kept on said disks prior to the creation of the RAID.
HTH!
At Thu, 10 Dec 2009 09:39:25 -0600 CentOS mailing list centos@centos.org wrote:
I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
If you can install 4 drives, eg you have 4 bays and 4 SATA connections, yes, it is easy. Just install the three new drives (to SATA port 2, 3, and 4), create the RAID-5 array (actually you'll need one small RAID-1 array for /boot, so you'll create two RAID sets: a small RAID-1 for /boot and the rest for the RAID-5) and copy everything over. You'll need to re-install grub (using grub-install) and then shutdown the machine and move the drive connectors around so that the new drives are 1, 2, and 3, and the old drive is 4 (or remove it completely), and start the machine up. You can then add the original drive as a hot spare disk (or not).
Matt _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Google "say no to RAID 5"
http://www.tomshardware.com/news/RAID-5-Doomed-2009,6525.html
Alan McKay wrote:
Google "say no to RAID 5"
http://www.tomshardware.com/news/RAID-5-Doomed-2009,6525.html
Say goodbye to whole-disk based RAID solutions and hello to next generation sub-disk RAID solutions, dramatically extending the real world lifetime of RAID 5(and RAID 6 which will become equally useless as RAID 5 is when drives get big enough).
http://www.xiotech.com/Products-and-Services_ISE.aspx http://www.3par.com/products/inspire_architecture.html#fgv http://www.compellent.com/Products/Software/Virtualization.aspx
(maybe more that I'm not aware of those are off the top of my head)
http://www.techopsguys.com/2009/11/24/81000-raid-arrays/
nate
On Thursday 10 December 2009, Matt lm7812@gmail.com wrote:
I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
In theory you can create a 3-drive RAID-5 with a "missing drive", rsync your filesystems over, and then repartition and force the existing drive to rebuild in.
You can't boot off a RAID-5, so you'll need to put /boot on a separate partition, also preferably raid-1'd on at least 2 of the drives.
It's not terribly hard but it's possibly to mess up and nuke your good drive before you're ready, so you should have a full backup on yet another drive anyway, and if you have that you might as well just build up a new system on the 3 drives and then restore your old filesystems over it.
On 12/10/2009 10:39 AM, Matt wrote:
I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
Moving to RAID-1 is going to be fairly easy. Moving to RAID-5 or RAID-6 will be a good bit trickier.
You're going to want a good bare-metal backup (maybe Mondo Rescue http://www.mondorescue.org/) before you get started.
Then your basic process is going to be:
- make sure that mdadm is loading - partition the new 500GB disks similar to the old disk - build mdadm raid1 arrays on the new 500GB disk (with 1 drive missing) - copy your files over (cp -a) - make sure grub is on the new disk - change your fstab on the new disk to mount the arrays (/dev/mdX) instead of the partitions (/dev/sdaX) - remove the old disk and see if you can boot up on the new one
I'm sure I'm forgetting something, just remember that you'll want to make lots and lots of backups (on a 3rd and 4th disk). And be ready to rebuild or restore from the bare-metal backup if you screw up.
I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
Moving to RAID-1 is going to be fairly easy. Moving to RAID-5 or RAID-6 will be a good bit trickier.
The more I hear I am thinking moving to RAID-1 would be fine. Is there a basic howto somewhere for that?
Thanks.
Matt
Matt wrote:
I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
Moving to RAID-1 is going to be fairly easy. Moving to RAID-5 or RAID-6 will be a good bit trickier.
The more I hear I am thinking moving to RAID-1 would be fine. Is there a basic howto somewhere for that?
I've seen a howto about converting an existing disk, but I'd do it by creating matching RAID1 partitions with one of the devices 'missing', then copying the existing data over, installing grub on the new disk, then swapping drives. Once you are sure the new copy is good you can add the old partitions to the raid devices and let them sync up. If your grub install turns out wrong you can always boot the install disk in rescue mode to fix it.
On a second thought, I'd probably install Centos 5.x on the new disk, then copy the old stuff back. It's pretty late in the cycle to spend much time fixing a 4.x system.
I have CentOS 4.x installed on a single 500GB SATA drive. Drive is about 10 percent used. I would like to migrate to software RAID 5 without reinstalling the OS. Was thinking 3 500GB drives. Is that possible or must I reinstall?
Moving to RAID-1 is going to be fairly easy. Moving to RAID-5 or RAID-6 will be a good bit trickier.
The more I hear I am thinking moving to RAID-1 would be fine. Is there a basic howto somewhere for that?
I've seen a howto about converting an existing disk, but I'd do it by creating matching RAID1 partitions with one of the devices 'missing', then copying the existing data over, installing grub on the new disk, then swapping drives. Once you are sure the new copy is good you can add the old partitions to the raid devices and let them sync up. If your grub install turns out wrong you can always boot the install disk in rescue mode to fix it.
On a second thought, I'd probably install Centos 5.x on the new disk, then copy the old stuff back. It's pretty late in the cycle to spend much time fixing a 4.x system.
I am thinking that way too. Even though everything is running perfectly fine on 32bit 4.x right now moving too 64bit 5.x would be much better. Was thinking upgrading to RAID1 would let me wait and do that at my leisure though. Reinstalling and moving all this too 5.x is no small task though. Yuk.
Matt
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