[TriLUG] upgrading a software (md) RAID

[Ron Kelley]

I look at it from a risk-vs-reward perspective.  Yes, I could swap  
them out one-at-a-time, but why take the risk of loosing any/all data  
due to a bad drive.  I much prefer to keep my original array in tact  
than to risk losing any data.  True, a RAID setup can survive a bad  
disk, but again, why take the risk?

Unless you are very short of drive cage space or power, I would  
migrate from one array to a new array.  If I lose any drive in the new  
array, no big deal - the original data is still in tact and I did not  
mess with the original array.

BTW - I give this recommendation based on a home-server perspective.   
I you had a server in a data-center with good backups and enterprise- 
class hardware, doing the one-at-a-time method might very well be the  
best option (as you can't easily install [or afford] a new NAS/SAN  
chassis in your rack).

Just my humble opinion.  Again, risk-vs-reward.


-Ron






On Oct 5, 2009, at 5:54 PM, Brian Cottingham wrote:

> If you waited a couple of days between each drive swap to make sure  
> the new drives worked, wouldn't the drive-swapping method be just as  
> reliable? Isn't half of the point of RAID to handle bad drives? I'd  
> like to understand what difference between the two methods inclines  
> the swapping method to a "fatal" failure, since the extra drive bays  
> needed for the rsync approach aren't always available.
>
> -Brian
>
>
> On 10/05/2009 04:13 PM, Ronald Kelley wrote:
>> Honestly, I would install the new drives, build the new array,  
>> create your partitions/filesystems, then rsync the data over.  Let  
>> it run for a few days before removing the 500G drives just to make  
>> sure you don't have any hardware problems with the new drives.
>>
>> Doing the one-by-one approach is time consuming and be fatal if one  
>> of the new drives is bad.
>>
>> Hope this helps...
>>
>>
>> -Ron
>>
>>
>>
>> On Oct 5, 2009, at 4:06 PM, Charles Mangin wrote:
>>
>>> i've currently got my home network server running a three drive  
>>> RAID system. it's running md (software RAID) under Fedora 11.
>>>
>>> the drives in there are 500 gigs, and with the prices of 1+ Tb  
>>> drives coming down so low, i'd like to increase capacity. ideally,  
>>> i'd like to do it without having to migrate my data to some  
>>> intermediary device while i build a whole new RAID.
>>>
>>> is there a good tutorial (that i've yet to find by googling) that  
>>> has a good step-by-step on how to do this? the process, as i  
>>> understand it, is to replace one drive at a time, rebuilding the  
>>> array each time. once all the larger drives are in place, the  
>>> final rebuild will show the new capacity. there's bound to be some  
>>> mdadm fiddling necessary as well...
>>>
>>>
>>>
>>>
>>>
>>> Charles Mangin
>>> Option8, LLC - Making Macs happy since 1999.
>>> option8 at option8.com | http://www.option8consulting.com
>>> mobile: 919.368.7167
>>> skype: option8llc
>>>
>>>
>>>
>>>
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>>
>>
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