Originally Posted by PeterO
Hi Melgross. Thanks for the insight.
Say, I have a question that perhaps you wouldn't mind shedding some light on; or, perhaps you might know where I might find further details. It concerns the impact an update has on OS X's footprint on a hard drive. The cumulative size of the incremental updates (10.5.0 to 10.5.1; 10.5.1 to 10.5.2; 10.5.2 to 10.5.3; etc.) seems to really add up. Do you know the relationship between the size of a downloaded update and the growth of OS X's footprint on a hard drive?
For instance (all hardware specs and language being equal):
Does the size of OS X increase by the size of an update? For example, will a system running 10.5.5 grow by 372MB after the 372MB 10.5.6 download update is installed and the .dmg file is deleted (a one-to-one relationship)?
Since the download is an image, presumably it contains compressed files. As such, might an update after its install routine finishes increase OS X's footprint by more than the size of the .dmg file?
Also, when using the Combo Update to span more than one generation of updates, how does the OS X footprint vary with the number of generations it spans? For example, will migrating from say, 10.5.4 to 10.5.6 be smaller than from a system migrating from say, 10.5.2 to 10.5.6? Alternatively, as presumably only the requisite files are tapped from the 668 MB Combo Update to bring the OS to 10.5.6, wouldn't the net size of the OS X footprint -- with some self-install cleaning/housekeeping -- be the same, as 10.5.6 is 10.5.6 across the board?
I'm sure this is a Pandora’s box to answer in detail but if it's not too much trouble, can you provide some broad strokes?
It's an interesting question.
It depends on what Apple is doing with the update.
If they are just fixing problems, the size may not vary much. If the code requires additions, then it will expand.
The size of the update doesn't directly give any indication of the final size. Apple will usually rework an entire file for an update, and replace the older one with the newer one. There could very well be a difference in size.
How many files are changed will affect the final size. If Apple is adding some features, as they often do, though minor, that could add to the final size as well.
Sometimes, when an update comes out, it doesn't replace everything, but may add new files to what is already there, so you do get a direct addition to the size from that.
Sometimes older files are left.
A Combo update is usually better, because it replaces all files with entirely new ones from the time of the original upgrade. This results in a cleaner upgrade, and is why it's usually better, which is, of course, why Apple offers it, in addition to it's being easier if you've missed one or more in the middle.
This is very complex, and the results will vary. The reason why the Combo is so much larger, as I've hinted, is because it contains ALL the files updated since the base OS upgrade.
What will the result be? It's hard to tell. I've seen the overall size get smaller with a Combo, as opposed to the incremental updates, and the other way around as well.
There are other factors involved in this. You may have noticed that the incremental updates vary in size depending on the model computer you have. Different computers use different parts of an update, though the core functions being updated are the same.
When using Software Update, Apple determines which model you have, and downloads the appropriate version. The Combo is the same. There's only one. But when it's updating your computer, it will again, update only what your computer needs, though it will, of course, do it from the beginning.
Also, depending on just what software you have apart from the OS, Apple may update with files to benefit them, whereas your friend, who has the exact same model you have, will not get those files installed, as she doesn't have that software. Some of that pertains to Final Cut Studio, and others. It won't be downloading updates to those programs, but to support files in the OS that work with those programs.
As you can see, it can be difficult to tell exactly what the result will be. I'm not sure where to go to find out more from Apple. I've never had this question asked before. Apple will tell what has been updated, but not in that detail.
Perhaps a software developer on the forum will know more.