updated 06:54 pm EDT, Tue July 30, 2013
New utility optimizes file structure, fixes performance on first Nexus 7
While Android 4.3 at first glance contained few outward-facing improvements, reports have surfaced that the new revision has implemented a SSD maintenance routine, TRIM, responsible for controlling which storage blocks are not currently in use by the file system. This implementation has revived some previously poorly functioning original Nexus 7 tablets, and has boosted performance in other devices.
When a file is deleted from SSD media, the data still is retained on the medium, but record of the file is purged from the OS. SSD firmware will use blank sectors in the interest of speed before it uses previously occupied sectors. The TRIM command (or fstrim, in the case of Android), in essence erases the previously used sectors when the device meets certain criteria, to keep the SSD tidy and operating at maximum efficiency.
According to the report at Anandtech, the Android framework starts the fstrim procedure when the device hasn't been touched for over an hour, no maintenance event has been sent in 24 hours, and the device is either on battery power with more than 80 percent of power remaining, or plugged in with more than 30 percent.
Users who have just upgraded to Android 4.3 won't see immediate improvement in file transfer speeds. After the utility has been invoked a few occasions with little user file structure modification between executions, only will the user see the benefit of the new routine.
The Android 4.3 upgrade won't be a panacea to all users. First of all, the update must be supported by the device manufacturer. As it currently stands, only a limited amount of Android-driven devices can receive the update. Second, the eMMC controller on a device with the update needs to support the TRIM command. Some scattered reports persist of the command either not existing or not executing, even on a Nexus-branded device. Reports have circulated of more than one version of the eMMC controller on different production batches of the device, which may be the cause of the latter reports.