Fedora and LVM

For that case I first shrink the fs as much as possible, to size X say. Then I shrink the LV to desired size Y, where Y is unambiguously > X. Then I resizefs without args to increase the fs back to the full size of the LV.

That I do it that way is probably cause I pretty much never shrink fses, and the last time I had to do this was way back, when LVM was still newish and e2fsadm and/or the --resize option didn't exist, or didn't handle this.

Generally LVM lets me manage fses in such a way that I only allocate to them what is reasonable for the foreseeable future. I keep the extra space free in the VG. As/when fses need more space, I just extend them. That this is so painless to do with LVM and resize2fs - online and without interruption - makes it the best way to manage storage, I find.

So so so so much better than the olden days, when you had to rejiggle partitions, reboot several times, and potentially use your swap device as a temporary root, in order to shift space to where you needed it. That was hair-raising, and I never want to go back to that! There isn't much to LVM, it didn't take much to learn, and it's removed a lot of stress.

One lesson though: snapshots need attentive monitoring. Never let a snapshot get anywhere near full, otherwise you risk it getting full and your box will wedge! Also, the early implementations of pvmove were very risky. Apparently those problems have been ironed out and it's now a lot more reliable, but I'm conservative and tend to avoid it. Luckily, that's easy - just move PVs the old fashioned way, copy them like you had to do with FSes before LVM. ;)

Overall though, LVM is a massive win over what went before.