[kwlug-disc] Swapping drives on server

unsolicited unsolicited at swiz.ca
Sat Jan 16 00:01:05 EST 2010

If you have raid, you have space for a temporary spare non-raid disk. 
As John says, you'll always have your original disks.

If you're willing to take the down time ... if you pop a temporary 
non-raid drive in of sufficient size, mirror the raid to it. Perhaps 
with Mondo (if that's even necessary, if non / on RAID / separate boot 
drive?). Then put your new disks in, initialize the raid. Copy from 
temporary drive back to new raid, remove temporary drive.

The problem with sticking the 135 GB disk in for one of the 73's is 
your 135 will instantly become a 73. All disks must be of the same 
size - introduce a new, larger one, and it will make the new one the 
same size as the old. Wasted space. Unless your RAID is JBOD, which I 
suspect not.

If you have the case space, cable connectors, and a powerful enough 
power supply, doing as John says, adding the 3 as a separate RAID, 
then mirroring, then removing, will save you some steps over the 
temporary drive above.

john at netdirect.ca wrote, On 01/15/2010 5:14 PM:
> kwlug-disc-bounces at kwlug.org wrote on 01/15/2010 04:48:25 PM:
>> From: "Insurance Squared Inc." <gcooke at insurancesquared.com>
>> OK, so lets say I make this swap. the last upgrade I'd like to do is
>> my hard drives. 
>> Does anyone have experience with upgrading the HD's in a linux raid?
>> I've got a 73 gig with the OS installed in it, and 2 73gigs running 
>> raid with my /home directory running on it.  I want to make those 2 
>> 73 gig hd's actually be my two 135gig hd's. 
>> Can I just pull drive 3 and install a 135 gig, wait for the rebuild,
>> the pull drive 2, install a second 135 gig,wait for the rebuild, and
>> done?  then when things settle down go into my config utility and 
>> resize the drives?
>> that's the way it's supposed to work right?  that's why I've got 
>> raid running on my production servers?  or should I forget about 
>> upgrading my hard drives and go back to sleep? 
> There are going to be three issues. First you want to move the data from 
> the 72GB set to the 135GB set, then you need to expand the file system, 
> then you need to set the boot sectors.
> Resizing the partitions is easy if you are using Logical Volumes and a 
> file system that can be resized online like a ext3. You're home directory 
> can be resized by taking it off-line first. Root file system needs online 
> (or boot into a live CD.) /usr and /var can be tricky too.
> Linux RAID is configured for partitions and so it doesn't mirror the boot 
> sector information. This is something you would have to change as well.
> I'm pretty sure you can create a three or four set mirror so you can 
> mirror your data to the new disk set. Then remove the 73GB disks from the 
> mirror. You still have to fix the boot sectors though.
> Once idea is to use something like mkcdrec or mondo and create a rescue 
> set. You would need a large enough off-line storage to accommodate, like a 
> series of DVDs. Then put the new disks in and run the rescue. The benefit 
> of this is that you have an easy back-out plan. If something doesn't work 
> just put the old disks in. Mkcdrec and mondo would be useful for your 
> system disks. Your data disks can be done by manually moving data.
> This type of scenario is a little scary. I rarely do something like this 
> that doesn't require a rescue disk and some serious grub-install or mdadm 
> work. That might just be because I don't read the instructions. Or it 
> could be because there are many ways to configure disks and file systems 
> that there isn't a one-size-fits-all solution.
> I learned a long time ago how to fix non-booting Unix/Linux systems and it 
> has removed much stress in my life. It's reasonably simple and it's made 
> failed upgrades and disk migrations like this nothing more than a 
> nuisance. Are my presentation slides on on this topic on KWLUG?
> John Van Ostrand
> Net Direct Inc.
> CTO, co-CEO
> 564 Weber St. N. Unit 12
> map
> Waterloo, ON N2L 5C6
> john at netdirect.ca
> Ph: 866-883-1172
> ext.5102
> Linux Solutions / IBM Hardware
> Fx: 519-883-8533
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