[CentOS] Re: software raid

Mon Apr 2 17:14:38 UTC 2007
Scott Silva <ssilva at sgvwater.com>

Les Mikesell spake the following on 4/1/2007 11:37 AM:
> Jeff Lasman wrote:
> 
>>> if the hardware can hotswap then you should be ok if i am reading
>>> what les said correctly.
>>
>> From time to time (not now) I have a machine on my testbed I can test
>> this on.
>>
>> Should I break the software RAID first?  I'd think so.
> 
> No, you'd expect a failure to automatically kick the drive out of the
> raid and go on about its business.
> 
>> Do I have to remake the RAID automatically?  I'd think so.
> 
> Yes, you have to 'mdadm --add ...' to make the replacement sync back up.
> 
>> Can I physically damage either drive?
>>
>> I'd think not.
>>
>> So I'm not sure I understand the problem as long as the (sata) drive
>> is in a hotswap bay.
>>
>> Anything I'm missing?
> 
> The question is whether the kernel will notice the new drive when you
> add it.  It might be possible to swap in an exact match and get away
> with the setup detected at boot time but that doesn't sound very
> healthy.  Can you hotswap a new SATA drive that wasn't present at boot
> time and have the kernel notice the new drive device and its partitions.
> If the partitions are recognized, mdadm will be able to add them.
> 
I think you would need a hot-swap capable controller also in addition to the
hot swap drive cage. Some controllers can be made to re-scan the bus, some
can't. But a card that is designed to support hot swap will have this feature.


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