launchd hitting every modified file every 30 seconds
I had the same problem a while back but IIRC, it turned out to be the Spotlight indexing services (mds, mdworker, etc) which are spawned by launchd.

Open Spotlight in System Preferences, switch to the Privacy tab, then drag your home folder into the window.  This will cause Spotlight to ignore your home folder and all subfolders.  

If you don't want to exclude all your files, create a folder specifically for this high I/O application and configure Spotlight to ignore just this folder.

For a geekier method, here are some shell commands to run that will exclude the entire drive from Spotlight indexing.  I use these commands on all external USB/flash drives as soon as I can.

Touch these files at the root of the drive to exclude, so
cd / for the main internal drive or cd /Volumes/USB_FLASH_DRIVE_NAME for an external USB/FLASH drive, then

sudo /usr/bin/touch .metadata_never_index
sudo /usr/bin/chflags hidden .metadata_never_index


and to stop prompting if you want to use the disk for TimeMachine backups

sudo /usr/bin/touch .com.apple.timemachine.donotpresent
sudo /usr/bin/chflags hidden .com.apple.timemachine.donotpresent