[Gllug] RAID Partitions

[Martin A. Brooks]

Hi Bruce,

On Friday, May 7, 2004, Bruce Richardson wrote:
> On Fri, May 07, 2004 at 05:08:50PM +0100, Martin wrote:
>> Hi Tethys,
>> 
>> On Friday, May 7, 2004, Tethys wrote:
>> 
>> > I'm not entirely sure what you're trying to say here. Under what
>> > circumstances would you want to be accessing a RAID device when
>> > your operating system isn't running?
>> 
>> To rebuild, recontainerise.  To add/remove hot spares.  To migrate
>> from one RAID level to another.  To extend, expand or shrink an array.

> Amazingly, with software RAID you can do most of this while the
> operating system is running.

Hardly amazing at all, hot spares require much of this. It's the
things you can't do that make the difference.

>  Still not seeing how this is unreliable
> compared to hardware raid.

For one, a hardware raid set will reconstruct itself onto a hot spare
regardless of whether or not the operating system is running or has
halted or has crashed.  With software RAID you end up with a RAID set
in an inconsistent state.


>    By the way, if you add spares while the
> operating system isn't running, that isn't "hot".

It was an example of what you can do with the operating system  not
running.  I wasn't making any judgements as to whether that's hot,
cool or tepid.


--
Martin A. Brooks, Clues Ltd.
http://www.clues.ltd.uk/

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