Re: [Libguestfs] [PATCH libnbd] copy: Implement destination preferred block size
On Sun, Jan 30, 2022 at 12:45:37AM +0200, Nir Soffer wrote:
On Fri, Jan 28, 2022 at 10:37 PM Richard W.M. Jones
<rjones(a)redhat.com> wrote:
> + .get_preferred_block_size = nbd_ops_get_preferred_block_size,
Why preferred block size and not minimum block size? For example if we
write 256k when the minimum block size is 64k, wouldn't qemu block layer
handle the write properly, creating 4 compressed clusters?
My theory was that if the destination prefers a particular block size,
and we're going to all this effort anyway, we might as well use the
preference. For the qcow2/compress filter the two values are
identical.
When not using a compress filter, qemu-nbd reports block size of 4k,
and
using this value it will kill performance.
Not sure I understand?
Rich.
--
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