When Google described Android 4.3 to the press at its press-meet last week, it missed out what is perhaps the operating system's biggest feature change over Android 4.2. It's discovered that Android 4.3 can issue TRIM command to storage devices. This should have a profound impact on storage performance.
TRIM is a garbage collection feature that helps negate write performance reduction in flash-based storage devices, that result from deleting and re-writing data. Unlike on magnetic storage devices like hard drives, where fresh data can simply be overwritten on parts of the media that has previously deleted data; deleting or rewriting data on a flash-based storage device entails electrically erasing and reprogramming NAND flash cells, which causes a reduction in write performance. TRIM negates this by marking deleted data for the SSD controller to erase while the device is idling, making sure cells holding deleted data are erased and ready to be written on, at the rated speeds.
An increasing number of smartphones and tablets use SoCs with eMMC and ATA SSDs that technically support TRIM, but lacked support from Android, until recently launched version 4.3 "Jelly Bean." Anandtech discovered that older Google Nexus devices, which recently received Android 4.3 updates, like Nexus 7 (2012), and Nexus 4, showed higher storage subsystem performance after their operating system upgrade.