[CentOS] Re: software raid

Tue Apr 3 00:16:27 UTC 2007
William Warren <hescominsoon at emmanuelcomputerconsulting.com>

of course if you need a card to do this then you don't need MD 
raid(unless the card is a FRAID card)

Scott Silva wrote:
> 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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