[mythtv-users] An LVM'd drive died! What do I do...

[chris at cpr.homelinux.net]

On Thu, Oct 27, 2005 at 01:41:28PM +0900, David Bennett wrote:
> I have seen the same article about reducing the size on LVM... I guess
> I'm just unclear about what I would lose if I lost an LVM'd drive
> (stemming from the fact i dont know how LVM data is stored.) Are bits
> of one file stored across multiple drives, or would the loss of a
> drive result in the loss of complete files?

It depends.  When you build an LVM you have a choice 
between linear or striped layout.  Linear allocates data 
sequentially from the beginning of the first drive through 
the end of the last drive.  Striping writes the data in 
chunks, rotating between drives in sequence.  Striping 
generally improves performance, but striped sets can't be 
extended whereas linear sets can grow.  In the event of 
disaster it's probably easier to recover data from the bits 
and pieces of a linear set, although it wouldn't be easy.

LVM and software RAID both use block devices and present 
themselves as block devices, so it's possible to layer them 
to achieve almost any desired level of flexibility and 
reliability.

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