Eric at on 4 Mar 2013 17:55:44 -0800

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Re: [PLUG] Survey: Linux RAID mirror sync time

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Short answer:  I don't think so.

Longer answer:  You have to use fdisk to change the partition type to "Linux RAID Autodetect".
I believe that process will likely wreck the data already on the drive.

Caveat:  I have not tried this.

I will be trying something similar on Wednesday with a system that was supposed to be set
up with RAID mirroring but was not.

I'm planning on trying this:

  Make backups.
  Put a new blank drive in the machine and setting up a RAID mirror with only that drive.
  Copy the existing data from the old drive to the new (half) RAID array.
  Format the old drive to be exactly like the new drive.
  Add the old drive to the array as the second drive.

I think the hard part might be the boot process and I might end up having to do some Grub
editing.  I'll let you know how it works (or doesn't).


On 03/04/2013 08:17 PM, Casey Bralla wrote:
> Related question:  Can you simply add a second drive to a system to create a RAID mirror system?
> I've got a server that crashed last year and then I f'ed up the restore.  I'd like to add a RAID mirror, but thought I had to start off that way from a clean install.  is there an easy way to setup RAID on a running system?
> On Monday, March 04, 2013 7:36:59 PM Eric at wrote:
>> Just curious what folk's experience is with this. If you replace one drive of a RAID mirror pair with a blank drive how long does it take to sync?
>> Maybe 5 years ago I replaced a 160GB drive in such a configuration and as I recall the sync was about 2 hours. That was a 500 MHz Celeron with PATA drives.
>> I believe that faster drives (SATA and even SAS) and faster chip sets and bus speeds may cancel out the penalty of larger drive sizes.  I only ever had to sync a drive that one time so the data sample size is way too small :-)
>> Thanks, Eric - -- #  Eric Lucas #

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#  Eric Lucas
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