Free Space Required for Startup?

[gameguy3001]

Does anyone know what the minimum amount of free space that is required for you computer to startup/run correctly? I have been told that it needs at least a couple gigs but I have a mac thats worked fine with only 250 MB free, so I'm confused.

 

[Mitthrawnuruodo]

Mac OS X makes extensive use of Virtual Memory (VM), which requires free disk space on your startup disk, aka your boot volume. If you startup disk is nearly full, your Mac's performance will degrade considerably.

* See our "Problems from insufficient RAM and free hard disk space" FAQ to determine if you have sufficient RAM and free disk space to get the best performance from Mac OS X.
* For advice on increasing the available space on your hard drive, see our "Freeing space on your Mac OS X startup disk" FAQ.

[Source]

From the first link above:

As a general rule of thumb: if the Available space on your Mac OS X startup disk is less than 5 GB, it is time to free some disk space. We suggest 5 GB as an absolute minimum as it generally requires that much free space to perform an Archive and Install of Mac OS X and still preserve some free space for VM swap files. However, more free space is better. For example, users of FileVault may want to retain more free space than that occupied by their encrypted Home folder as one requires free space larger than your encrypted Home folder in order to disable FileVault.

[Source]

 

[topgunn]

My rule of thumb is that 5-10% of the system disk should be available.