Consequences of using >80% hard memory

It's fine.

That's not a problem. Many run for months at a time without restarting.

If you're talking about hard drive space, it's good to leave at least 10% free (more is better).

Performance Tips For Mac OS X

 

Btw, "memory" is not the same as "hard drive capacity":

• What is Computer Memory? RAM vs Hard Drive
• RAM vs. Hard Disk

It is recommended, to have 10 to 20 % of the HDD's capacity unused.

 

Whilst everything will work just fine, running with little free space means

- you are running into the slow part of the disk. the second half (roughly) of the drive is a lot slower than the first half due to lower data density (less data read per revolution of the disk).
- with less free space available, as you remove and re-add files, there will be less contiguous gaps of free space available, which will potentially increase file fragmentation. fragmented files take longer to read/write as the disk head needs to skip back and forth over different parts of the disk, and this takes time.


if you CAN free up space, you can potentially get disk access on the machine to be a little faster.

but - nothing will "break" from running a low amount of free space, unless you actually run out.


If you want to get your disk back into "optimal" condition after freeing up all that space (all the data at the start of the disk, on the faster part) - you could do a time machine backup and restore, but its a bit of screwing around for probably minimal gain.

 

I do recommend you download Onyx. It's a versatile program and you can do a lot of maintenance. Delete old caches, repair disk permissions, verify the disk (which Onyx does by default), and even opens up some parameters that aren't accessible by System Preferences and the Finder.

 

The biggest downfall of running with little free space (30-40GB is still ok, though) is that you have less virtual memory available to the system. Since Mac OS X makes use of a significant amount of virtual memory to keep everything running smoothly, it's going to affect performance. Until you get down to ~10GB free, you're usually gonna be ok, but it does depend on what you use your computer for.

jW