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Old 12-10-2009, 02:39 PM
Matt
 
Default Migrating to RAID

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
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Old 12-10-2009, 03:15 PM
James Bensley
 
Default Migrating to RAID

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!
--
Regards,
James

Joan Crawford *- "I, Joan Crawford, I believe in the dollar. Everything I earn, I spend."

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Old 12-10-2009, 04:23 PM
Robert Heller
 
Default Migrating to RAID

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
>
>

--
Robert Heller -- 978-544-6933
Deepwoods Software -- Download the Model Railroad System
http://www.deepsoft.com/ -- Binaries for Linux and MS-Windows
heller@deepsoft.com -- http://www.deepsoft.com/ModelRailroadSystem/

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Old 12-10-2009, 04:43 PM
Alan McKay
 
Default Migrating to RAID

Google "say no to RAID 5"

http://baarf.com/

http://www.tomshardware.com/news/RAID-5-Doomed-2009,6525.html





--
“Don't eat anything you've ever seen advertised on TV”
- Michael Pollan, author of "In Defense of Food"
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Old 12-10-2009, 04:58 PM
Alan Hodgson
 
Default Migrating to RAID

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.

--
"No animals were harmed in the recording of this episode. We tried but that
damn monkey was just too fast."
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Old 12-10-2009, 06:08 PM
"nate"
 
Default Migrating to RAID

Alan McKay wrote:
> Google "say no to RAID 5"
>
> http://baarf.com/
>
> 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


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Old 12-10-2009, 10:20 PM
Thomas Harold
 
Default Migrating to RAID

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.
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Old 12-10-2009, 10:26 PM
Matt
 
Default Migrating to RAID

>> 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
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Old 12-10-2009, 10:44 PM
Les Mikesell
 
Default Migrating to RAID

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.

--
Les Mikesell
lesmikesell@gmail.com




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Old 12-10-2009, 11:00 PM
Matt
 
Default Migrating to RAID

>>>> 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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