Re: raid5/lvm setup questions

Shane wrote:

On Mon, Aug 07, 2006 at 08:57:13PM +0100, Nix wrote:

quoted

On 5 Aug 2006, David Greaves prattled cheerily:

quoted

As an example of the cons: I've just set up lvm2 over my raid5 and whilst
testing snapshots, the first thing that happened was a kernel BUG and an oops...

I've been backing up using writable snapshots on LVM2 over RAID-5 for
some time. No BUGs.

Just performed some basic throughput tests using 4 SATA
disks in a raid5 array.  The read performance on the
/dev/mdx device runs around 180mbps but if lvm is layered
over that, reads on the lv are around 130mbps.  Not an
unsubstantial reduction.

Check the readahead at various block levels
blockdev --setra xxx

I think I found the best throughput (for me) was with 0 readahead for /dev/hdX,
0 for /dev/mdX and lots for /dev/vg/lv

I seem to recall patches to md floating around a couple
years back for partitioning of md devices.  Are those still
available somewhere?

man mdadm and see --auto...

David


--