[pve-devel] qcow2 bench and speed optimisations

Alexandre DERUMIER aderumier at odiso.com
Fri Sep 14 05:12:26 CEST 2012

I'm playing with qcow2 on my new netapp pnfs cluster,some optimisations can be done.

some benchmarks :

1).raw file : 20000io/s

2).qcow2 file, sparse : 300 io/s   :/

3).qcow2, preallocated metadatas (nosparse): 4000io/s

4).qcow2, with lazy counts + preallocated metadatas : 4000io/s. (lazy count is really only benefit for writethough)

1)qemu-img create -f raw -o size=10000000000 file.img

2)qemu-img create -f qcow2 -o size=10000000000 file.img

3)qemu-img create -f qcow2 -o size=10000000000,preallocation=metadata file.img

4)qemu-img create -f qcow2 -o size=10000000000,preallocation=metadata,compat=1.1,lazy_refcounts=on file.img

So I think it should be great to add an option for preallocatting metadatas, the boost is really huge.

Do you have any news about FVD ?

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