About the neccesity of a File System atop an LV
I just started using LVM a month or 2 ago when I was learning Xen Cloud Platform and love how flexible it is. I recently built my self a Fedora Desktop seperate from my VM server. When I was playing around with mounting a raid array to Fedora I relized that I could mount an LV directly without creating a file system on top of it. I was suprised as I though LV's were sort of like super partitions and not really a FS.
I started using the LV I created without an additional FS like ext4 and have had not issues or slow writes (that I can tell) but everyone says "You must then create a file system" after you make an LV before you mount it.
Why can I mount an LV directly and use it without a FS? Is LVM a type of FS? Are there any drawbacks or dangers in using LVM this way?