PE2850 RAID1 upgrade drives

Stroller stroller at stellar.eclipse.co.uk
Sat Sep 4 09:24:41 CDT 2010


On 4 Sep 2010, at 13:15, Raymond Kolbe wrote:
> ...
> 1) Create a Ghost image of OS/data, etc. for backup and restore.
> 2) Turn off the server and replace both drives with the newer 300GB  
> drives.
> 3) Turn on the server and create a new RAID1 array.
> 4) Restore the Ghost image from step 1.
> 5) Use gParted or another partition resizing program to increase my
> partitions.
>
> However, no one has confirmed that these methods worked for them.
>
> Now, both ways sound like they would work, but I am extremely nervous
> about this because I have also found forum postings and articles about
> having to manually copy over partition information, and that disk  
> block
> sizes matter, etc. (not exactly sure about the technical issues here),
> etc. This is also a mission critical production server so uptime is  
> key.
>
> So my question is, are either of the two methods above realistic,  
> and/or
> has anyone actually upgraded RAID1 in a PE2850 or PE server before
> without having to reinstall their OS?


I've definitely done this sort of thing with another model of  
PowerEdge, the 2800. I think I've done it with a 2850, although mine  
doesn't have the RAID key.

The drives will just appear to the o/s as block devices - if you boot  
from a LiveCD (well, as long as it's one that supports the RAID  
controller) you'll see the current array as (something like) /dev/sda.  
Take a note of the current configuration, just so you're completely  
confident (e.g. `ls -l /dev/disk/* > /mnt/floppy/file.txt`).

Shutdown the system, slap the new drives in (don't remove the existing  
ones), create an array of them in the RAID BIOS, and reboot again to  
the Live CD. You'll see the existing /dev/sda as it was before  
(compare /dev/disk/by-id/* with what you had before) and a new /dev/ 
sdb. The RAID controller consolidates the drives (hardware RAID) and  
presents them to the o/s as the single /dev/sdb block device.

You can simply `dd if=/dev/sda of=/dev/sdb`, shutdown the system,  
remove the original array, power up and change the boot device in the  
RAID BIOS and boot to the cloned system.

I personally don't use Ghost - Linux has `dd` which is perfectly  
adequate. I trust it more than Ghost. You can "ghost" to backup image  
file on an external USB drive with `dd if=/dev/sda of=/mnt/seagate/ 
file.img`. Nor do I use gParted, but the command-line parted. `sudo  
parted /dev/sda p` should show that the new array is larger. It can be  
a pain to manipulate in Linux the partitions of Windows Server, as  
I've mentioned in the past.

I'm tending to assume 2 system drives in a RAID1 here, so that you  
have enough empty bays for the two replacement disks. You can unmount  
and remove data arrays whilst you're upgrading the system drives. I  
perform all partition / filesystem resizes from the LiveCD, with the  
disks unmounted.

DON'T do this sort of thing on a production system without a backup.  
This mailing-list posting confers no warranty, express or implied. If,  
like me, you're a lone IT consultant working on a client's only  
mission-critical server (or even one of your own) this kinda stuff can  
be tremendously stressful. There is potential for you to foul-up at  
any time if you just once confuse your source and destination drives.

This demonstrates the need for backups constantly throughout the  
system's life - really, as soon as you've commissioned the system you  
should be taking backups, you should test them; you should do a full  
restore just to prove you can, before you have any important data on  
there. Of course there are many occasions when we are not so perfect,  
but this migration is perfectly manageable if you're careful; 99 times  
out of 100 there will be no problems, but it can be a bit nerve- 
wracking.

You ought to be confident about this before you start, so if you can't  
get (or afford) someone more experienced to help then my best  
recommendation is to practice it on another system first. I got my  
2850 at least 6 months ago, and they were going for less than £200 on  
eBay then - I wouldn't be surprised if they're less than £100 now.

This is a really straightforward migration that most of the guys on  
this list - or any other experienced Linux system administrator -  
would have no trouble at all with. I'm surprised you can't find  
"confirmation" of this working (although I think few of us would use  
Ghost, if that's part of your search criteria) because I think there  
are probably people doing this on a daily basis with no problems. But  
one can't write exact instructions for you at one remove like this -  
the block devices may be named differently on your system, for example  
as /dev/hda instead of /dev/sda, and of course there's the liability  
that a single tiny omission can foul you up. But, yes, this technique,  
generally speaking, does work.

Stroller.



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