[linux-lvm] some questions

Christoph Anton Mitterer calestyo at scientia.net
Thu Jul 18 18:43:00 UTC 2013


I'd have some questions...

1) Is the --discards option the same than the issue_discards option from
the config file? Since the one defaults to 0 the other to passdown?
If not what's the difference?

2) Of an existing LV, can I see how data was actually allocated? And how
can I see the alloc policy of a VG? vgdisplay doesn't show it.

3) Do I see that correctly, when I use Normal as alloc policy,... it
will try to do contiguous allocation... and only do not so,... if not

4) md_component_detection and md_chunk_alignment
Will these also work if there is another block layer (e.g. dmcrypt) in
between? Especially the md_chunk_alignment?

5) What alignments are needed?
"md_chunk_alignment — If set to 1, and a Physical Volume is placed
directly upon an md device, LVM2 will align its data blocks with the md
device's stripe-width."

Implies that something needs to be aligned to the strip width (I guess
you mean the chunk_size * number_of_data_chunks (i.e. not counting
What is that? Should the PEs be aligned to the stripe width? I.e.
multiple PEs exactly in one stripe, or multiple stripes exactly in one

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