[CentOS] Re: Rebuilding Raid 1
ssilva at sgvwater.com
Wed May 3 16:09:03 UTC 2006
Les Mikesell spake the following on 5/1/2006 9:32 PM:
> On Tue, 2006-05-02 at 00:13, Mace Eliason wrote:
>> I think the reason for the partitions not being on the same drive is
>> because the old drive is the bootable drive and I changed the scsi ids
>> of the drives to get it to work. I think it is using sba for the boot
>> but centos is on sbb.
> It doesn't really boot from raid. It loads the kernel from
> the underlying partition on the boot drive, then the kernel
> detects the raid devices and decides how to activate them,
> then it mounts them according to /etc/fstab. You should be
> able to review the detection process with 'dmesg |less'
> if you are interested.
>> I just need to make sure that the sync happens so that the info on sbb
>> is what is synced. The info on sba is 1 month old this I have confirmed
>> by mounting sba3 and looking at the dates of the last emails received on
>> the server I couldn't mount sdb3 because it is the active partition.
> Be careful with your spelling... I assume you mean /dev/sda3 is the
> old one.
>> So from what your saying below running mdadm as you have shown will it
>> copy the good info on sdb to sda?
> Again, be careful. It will copy the currently active partition
> to the one you are adding - so if you see the current version
> now, that's what will be mirrored. In the case of /dev/sdb3 it
> will go from sdb to sda. But /dev/sda1 is active now and will
> be copied to /dev/sdb1.
>> I have to have this server ready for 7am or we will loose this
>> contract. I can't believe I have spend all day on this.
> This is the sort of thing you should practice on a test
> box so you are prepared to handle an actual problem in a
> reasonable amount of time.
>> If I copy over the wrong info they will lose 1 months worth of emails.
> You can only copy from the active one to the one you
> add. And by the way, having backups can be a good thing
You might want to download the free Vmware server software and play with
senarios like this. You can create installs with 2 drives in raid 1, and kill
a drive and play with rebuilding. All virtual, so no damage to working
systems. This is how I learned some of the nuances of linux software raid.
MailScanner is like deodorant...
You hope everybody uses it, and
you notice quickly if they don't!!!!
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