[linux-lvm] deleted LV recovery: understanding metadata format and determining LV extents

[Thanos Makatos]

> > know how to interpret the "stripes" member. These are all linear LVs.
> >
> >     stripes = [  "pv0", 306705     ]
>
> do the values make sense from a 512byte block point of view? Either as extent-size * #extents = size in 512kb blocks,
> or as an absolute offset from the beginning of PV0 device? or it might be the offset in extent-size from the beginning
> of the PV0 data area. Yeah, it's probably that.

I don't think these units are expressed in anything else but extent size units (http://tldp.org/HOWTO/LVM-HOWTO/pe.html).

I did the following test: I created two LV and compared the LVM metadata against the output of lvdisplay -m, here's what I got:

First volume, LVM metadata:
segment1 {
	start_extent = 0
	extent_count = 256
	type = "striped"
	stripe_count = 1
	stripes = ["pv0", 2568]
}
First volume, lvdisplay -m:
--- Segments ---
Logical extent 0 to 255:
  Type                linear
  Physical volume     /dev/sda3
  Physical extents    2568 to 2823

Second volume, LVM metadata:
segment1 {
	start_extent = 0
	extent_count = 2567
	type = "striped"
	stripe_count = 1
	stripes = ["pv0", 1]
}
Second volume, lvdisplay -m:
--- Segments ---
Logical extent 0 to 2566:
  Type                linear
  Physical volume     /dev/sda3
  Physical extents    1 to 2567

Or have I got it completely wrong?