[pve-devel] [PATCH qemu-server] fix #3324: clone disk: use larger blocksize for EFI disk when possible

[Fabian Ebner <f.ebner@proxmox.com>]

Moving to Ceph is very slow when bs=1. Instead, use the biggest possible power
of two <= 1024. At the moment our EFI image sizes are multiples of 1024, so
just using 1024 wouldn't be a problem, but this feels more future-proof.

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
---

I did not see an way for 'qemu-img dd' to use a larger blocksize while still
specifying the exact total size if it is not a multiple of the blocksize.

 PVE/QemuServer.pm | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index f401baf..e579cdf 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -6991,7 +6991,15 @@ sub clone_disk {
 		# that is given by the OVMF_VARS.fd
 		my $src_path = PVE::Storage::path($storecfg, $drive->{file});
 		my $dst_path = PVE::Storage::path($storecfg, $newvolid);
-		run_command(['qemu-img', 'dd', '-n', '-O', $dst_format, "bs=1", "count=$size",
+
+		# Ceph doesn't like too small blocksize, see bug #3324
+		my $bs = 1;
+		while ($bs < $size && $bs < 1024 && $size % $bs == 0) {
+		    $bs *= 2;
+		}
+		my $count = $size / $bs;
+
+		run_command(['qemu-img', 'dd', '-n', '-O', $dst_format, "bs=$bs", "count=$count",
 		    "if=$src_path", "of=$dst_path"]);
 	    } else {
 		qemu_img_convert($drive->{file}, $newvolid, $size, $snapname, $sparseinit);
-- 
2.20.1