et lux in tenebris lucet

I can across this that’s worth sharing regarding LVM snapshot performance pitfalls. The trick is chunk sizes, although ultimately it’s still copy-on-write.

http://www.nikhef.nl/~dennisvd/lvmcrap.html

I never use LVM snapshots long term anyway; just freeze fs, snapshot, unfreeze fs, do whatever, destroy snapshot. Another trick is to put the snapshot on a physically separate device from the source LV. Although you’ll still see a performance impact, it will be a bit less since you aren’t driving the disk seek rate through the roof.