I am testing out a system in which each Guest disk is mapped to a LUN on a backend storage. I am using Xenserver 6.5 for this and creating an SR with a single VDI inside it for each Guest disk. The way it would work is, from an LVM point of view, I would have a Volume Group (VG) for each virtual disk and a single logical volume (LV) inside that VG. What I am seeing is that creating new volume groups is taking a lot of time. In my test after creating about 600 volume groups, it took about 4 seconds to create a new one. I have observed this to be a linear trend where the more VGs I add the slower future operations become. Other operations like getting the logical volumes inside a VG have also slowed down (even though there is only 1 LV per VG).