explai ned… The tools you’ll use
monitoring for internal and Thunderbolt drives; USB or FireWire drives can only be monitored by installing third-party extensions. Disk Utility provides only basic monitoring, and more thorough checking requires a third-party tool such as DriveDx (£17.68, binaryfruit.com). Good status is no guarantee a disk won’t fail in the next instant, just a statement that the chances are very low.
Modern storage types
SSDs have no moving parts, but their memory chips can be written to a set number of times before they start to fail. In practice, that limit is beyond the life of most people’s Macs. However, it’s wise to avoid actions that write more to an SSD than is strictly needed, and defragmenting one is pointless and wasteful.
Ensure the TRIM feature is active; it allows the blocks used by deleted data to be reset to a fresh state, and improves performance. It’s enabled for Apple’s flash storage by default; for other SSDs, the maker should disclose whether it’s handled in hardware; if not, the command sudo trimforce enable (in OS X 10.10.4 or higher) enables OS X’s software implementation for third-party flash storage.
Fusion Drives, fitted by Apple in iMacs and Mac minis, or made yourself (see MF296, p64) need care for the hard disk component, but OS X should keep them working efficiently. Many third-party apps do not yet work fully with them, so disaster recovery can be tricky.
Networked storage normally uses one or more hard disks but must be managed through its own software, which often has very limited maintenance facilities. Apple’s Time Capsules are managed using AirPort Utility, which lacks manual check and repair commands. So, you can do little to care for them, and failure is usually fatal.
End of life
Storage has a life cycle which must be planned for from the outset. Careful choice rather than impulse buying will meet your needs better. Now that OS X supports huge volume sizes, there are few benefits to partitioning large drives into several smaller volumes, although Time Machine backups are best given their own volume to guarantee their size and life.
When drives fail or are replaced, ensure no one else can recover data from them: use Disk Utility to erase and overwrite them mulitply if you can spare the time. It’s generally thought that the more cycles you can manage, the less likely it is anyone will be able to recover data. Finally, use a sledgehammer to render a drive physically unusable before disposing of it.