[pve-devel] [PATCH qemu-server] add discard_granularity to 4M for rbd storage

[Alexandre Derumier]

when we have snapshots on rbd and do a trim, the space is increasing
http://tracker.ceph.com/issues/18352

we need to trim a full object (4MB by default), to be able to free space.

test:

without discard_granularity
---------------------------
vm-107-disk-1		                                       20480M   2500M
vm-107-disk-1                                                  20480M   2500M

vm-107-disk-1 at snap1                                            20480M   2500M
vm-107-disk-1                                                  20480M  90112k

vm-107-disk-1 at snap1                                            20480M   2500M
vm-107-disk-1                                                  20480M   1020M

with discard_granularity=4M
---------------------------
vm-107-disk-1		                                       20480M   2500M
vm-107-disk-1                                                  20480M   2500M

vm-107-disk-1 at snap1                                            20480M   2500M
vm-107-disk-1                                                  20480M  90112k

vm-107-disk-1 at snap1                                            20480M   2500M
vm-107-disk-1                                                  20480M    144M
---
 PVE/QemuServer.pm | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 6a355f8..fd9754c 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -1695,6 +1695,11 @@ sub print_drivedevice_full {
 	$device .= ",serial=$serial";
     }
 
+    my $volid = $drive->{file};
+    if($volid && $drive->{discard}) {
+        my $storage_name = PVE::Storage::parse_volume_id($volid);
+        $device .= ",discard_granularity=4194304" if $storecfg->{ids}->{$storage_name}->{type} eq 'rbd';
+    }
 
     return $device;
 }
-- 
2.11.0