Re: mdadm does not create partition devices whatsoever, "partitionable" functionality broken

[Roman Mamedov <rm@romanrm.ru>]

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On Sat, 14 May 2011 12:10:56 +0200
David Brown <david.brown@hesbynett.no> wrote:

> What is perhaps more relevant, is can filesystems see the fragmentation 
> of the LV's?  I don't know the answer.

No, of course they can't.

> Still, you don't usually have many segments in an LV - if you want the 
> LV to be fast, you can request it to be contiguous when creating it. 
> Then you only get a fragment for each time it is grown.  It's a price 
> often worth paying for the flexibility.

From what I see, the key selling point for LVM is the ability to 'easily'
add/remove/resize LVs. And then if you buy that and start to actively use
these features, you end up in a situation (badly fragmented LVs) from which
there isn't a proper way out. No - backup and restore, or 'have enough
contiguous free space to mirror your entire LV and then nuke the original' are
not the answer. What's sad is that there isn't any fundamental technical
reason LVs can't be defragmented. They can, just no one has bothered to write
the corresponding code yet.

-- 
With respect,
Roman

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