Fri, 14 Dec 2012 How to speed up a Mac hard disk

To restart or not to restart

Few aspects of Macs cause more arguments than the one about what to do at the end of the day: shut down or sleep? The old argument of leaving a computer on as much as possible was based on the wear and tear of restarting the hard drive. Suffice to say that the restart argument rests on more than just this.

The main advantage of sleeping your Mac is to be able to continue where you left off quickly. But the disadvantages may outweigh this especially if you’re marginal on RAM. Mac OS X uses swap files, spaces on your hard disk that allow your Mac to pretend it has more RAM than it actually has, for virtual memory. Once the number of swap files exceeds five or so, your Mac starts to slow down. Time to reboot. Depending on your usage and RAM, this could be several times per day. MenuMeters (free, www.ragingmenace.com) shows the number of swap files along with free/used memory and other useful info. Rebooting also clears all system temp, swap and cache files. 

If you run maintenance or backup scripts at night, your Mac can always be set to shut down after these.

Instant feedback – use MenuMeters to see memory, processor and hard drive usage 

Emptying caches

Macs use a number of caches, small files retained on the hard drive with the intention of re-using them. As such, they increase the performance of your Mac. Some are controlled by the system, others by individual apps. For instance, a web browser will cache web pages so that when a website is revisited, the pages can be read from hard drive rather than re-downloaded.

The problem is that not all apps are well behaved in this area. Have a look at your user caches by hitting Command+Shift+G from your desktop to bring up Go To Folder and then typing ~/Library/Caches/. Don’t be surprised if a number of gigabytes are residing here. The biggest ones are likely to be for your web browser and the likes of Google Earth, iTunes and Spotify. As user caches are rebuilt when needed, you can safely delete these, especially for apps that are no longer used. Safari, Firefox and iTunes all allow you to clear caches directly within the apps. 

There are a number of useful utilities here including OnyX (free, www.titanium.free.fr) and Mountain Lion Cache Cleaner ($9.99, www.northernsoftworks.com). While both do far more than just deleting caches, they will allow you to keep your user caches under control.

OnyX has a host of useful features including cache control

Cleaning up your hard drive

Part of your Mac’s performance depends on empty hard drive space. It needs to be able to write and read its swap files and contiguous free space helps. This brings up the thorny issue of defragmenting. With the older Mac OS this was debatable but Mac OS X but has its own built-in safeguards that prevent files from becoming fragmented in the first place. This is probably the reason why there isn’t a defrag option in Disk Utility. But for these safeguards to work, you need at least ten percent of your disk drive empty. Replacing your hard disk with a larger capacity model is one answer but it will still fill up eventually. The answer is to offload some of your larger files. 

Your hard drive hosts a number of big files and folders. These include email files and backups, old versions of apps that you no longer need, and photos. But the single biggest folder is likely to be your iTunes library, especially if you have movies and mobile apps as well as music. Use WhatSize ($12.99, whatsizemac.com) or OmniDiskSweeper (free, www.omnigroup.com) to view your disk usage.

Free up disk space by offloading large files to an external drive. This includes your iTunes library which can be relinked via iTunes’ preferences/advanced tab.

Find your disk hogs with WhatSize