In Mac OS X you can use cron to schedule tasks but you can also use launchd. To use launchd to load or unload an agent where you’ve setup a task use the launchctl command. Here we will use launchctl to manually start a process given that we defined a plist called /Library/LaunchAgents/com.apple.OpenProgram.plist (where program is maybe the name of some program you want to fire up):
launchctl load Library/LaunchAgents/com.apple.OpenProgram.plist
Your application should fire up now. Do not quit it for ten seconds. Wait about 15, then quit it. Notice it start up again. This is because it is a launchAgent and will restart any time it is closed. Now run:
launchctl unload Library/LaunchAgents/com.apple.OpenProgram.plist
Watch your program close.
All volumes have a block size. In Mac OS X you can see a block size by entering the following command (assuming disk0):
sudo diskutil information 0
If you notice in the Total Size: field you’ll see the number of blocks followed by a block size. By default it is 512 bytes. One of the things that makes it possible to attain high performance from an Xsan volume is the ability for the block size to be customized. The general rule of thumb is that the Stripe Breadth and the Block size should multiply to equal 1MB. So if you have a block size of 256 then your stripe breadth should be 4.