updated 03:10 pm EST, Fri February 25, 2011
Mac OS X Lion shows TRIM support for SSDs
A finding in the developer preview of Mac OS X Lion has confirmed that the OS will have much needed support for auto-tuning solid-state drives. System Profiler now automatically detects SSDs with the TRIM command, and the OS now presumably uses the technique to clean up the drive. The MacGeneration investigation found that Apple's Toshiba-sourced SSD for the MacBook Air was already recognized, but third-party drives weren't yet enabled.
TRIM is meant to tackle a problem with performance degradation unique to flash-based storage. The drives aren't typically aware of the difference between an unused data block and one with fragments of deleted files and will often treat a write to one with fragments as an overwrite operation, slowing it down significantly. If unchecked, an SSD can gradually lose its performance as the drive fills up and as more and more erase operations leave fragments. If present, TRIM automatically helps clear out these blocks and lets the SSD write to them as though they were new.
Windows 7 has had the TRIM command built-in from the start and has been instrumental to the rise of the SSD market populated by drives from Corsair, Intel, OCZ and others that have focused on speed now approaching half a gigabyte per second, even on home-oriented drives. These SSDs will still work in Macs but lose the advantage with the current platform.
The implementation could be vital for the MacBook Air and any Mac either designed with or built to order with an SSD. While the systems are currently much faster for booting and app loading than Macs with spinning drives, Snow Leopard's lack of TRIM could lead the drives to gradually bog down and lose much of the initial appeal. Lion should keep these systems running at peak speeds and could encourage more explicit Mac support for SSDs from companies previously only courting gamers and other hobbyists.