Bug #67912 showed that role::labs::lvm::biglogs is fundamentally broken: You can't move around/shadow /var/log in a running system.
I thought about some super-duper OpenStackManager UI where you could specify the partitioning and during reboots OpenStack would shuffle the files and volumes accordingly, so that you always have a clean system, when Yuvi pointed out a far superior solution:
If we increase the size of the default /var partition by (for Tools, other projects may need more) 2 GByte, we wouldn't have to think about all that complex stuff, because (at Tools) /var/log is usually less than 2 GBytes big.
With the same step, we might want to set up a separate /tmp partition (could be even ramdisk) to avoid the problems of people filling that up as well.
This will require a bit of disk space at virt*, and it will not solve all partitioning needs there are at Labs, but I think it is a quick solution for 90 % that could last a long time.