The Tech Bench

Over the life of your Mac, there’s a good chance that you may see the following message:

This alert means that you either need to make some room on your hard drive (by deleting files) or upgrade to a bigger drive.

But how full is too full? And how much free space should there be on your hard drive?

Apple states that for optimal performance, 25% of the available hard drive space should be left free for the system to use. The system uses free hard disk space as virtual memory to help speed up and work with open files and apps.

While 25% may seem high, you can really start to notice the system slow down when you approach the 15% mark, especially when working with large files.

When the hard disk has less than 10% free space, the above message will pop up. If you add files until the disk is full, you risk complete data corruption (happened to me) and data loss.

The first step when you see the above message is to check for any duplicate files or for video files you no longer need (these tend to be some of the largest files) and delete them.

The next step would be to get a new, larger drive installed for your Mac.

[ MyService Hard Drive Upgrades ]

iMac 20" getting its HD replaced. Note the glass and front bezel are removed during the installation.

A failing hard drive (HD) is one of the most common ailments we see here at MyService.

Here are some of the symptoms to look for if you suspect the HD in your Intel iMac has failed or is failing:

No video or the machine turns off during boot

Yes, just like the new Unibody MacBooks, if the system detects a bad HD on boot, the system will shut itself down.

Grinding or clicking noises

This is the most common symptom we see. A noisy hard drive can often be the first sign that the drive is going to fail. There is a cool new (and free) iPhone/Touch app from DriveSavers that plays sounds of a failing hard drive.

Flashing “?” on startup

The system cannot find an operating system to boot off of (because the drive is damaged.)

Slow performance or missing files

If you notice the machine is getting much slower, files are disappearing or settings randomly change the drive may be on the way out.

So what do you do if these symptoms arise? If you can, back up your User folder first. The next step would be to take your Mac to your local AASP (like us:) for a diagnostic and service.

As part of our diagnostic, we boot using an external HD and test using Drive Genius. The hard drive replacement on the Intel iMac is a little involved (glass, bezel and screen are removed,) so we would generally not recommend a DIY on this one.

[ MyService iMac HD Replacements ]

The Sudden Motion Sensor (SMS) is a motion-based hardware system designed to protect the data on your hard drive.

Apple starting using the system in 2005 and by 2006 all Mac laptops incorporated the technology.

There is an accelerometer (similar to the iPhone) that detects sudden movement. Once the accelerometer detects sufficient movement, the system disengages the drive heads from the disk platters. Think of the hard drive as a record player that when dropped is told by the SMS to lift the needle off the record to keep it from getting scratched on impact.

There has been some confusion because some hard drives have similar technology built into the drive. Sometimes SMS needs to be disabled to allow these aftermarket hard drives to work so the systems do not cause a conflict (kernel panic.) Also other manufacturers like HP and Dell have similar technologies that go by different monikers.

While these sensors do not fully protect against data loss in an impact or fall, they definitely help reduce the chance of damage and loss.

Check out MacSaber for a fun application of the technology.