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.
Когда файл удаляется с твердотельного накопителя, физически данные остаются на нем, но ОС больше не учитывает данную запись. В результате на SSD накапливается «мусор», снижается его быстродействие - перед записью ячейки все равно надо очищать. TRIM очищает ранее записанные сектора заблаговременно, что дает прирост производительности.
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.