4.3值得升级啊

Android 4.3 having TRIM

Trim的作用
　　原本在机械硬盘上，写入数据时，Windows会通知硬盘先将以前的擦除，再将新的数据写入到磁盘中。而在删除数据时，Windows只会在此处做个标记，说明这里应该是没有东西了，等到真正要写入数据时再来真正删除，并且做标记这个动作会保留在磁盘缓存中，等到磁盘空闲时再执行。
　　这样一来，磁盘需要更多的时间来执行以上操作，速度当然会慢下来。
　　而当Windows识别到SSD并确认SSD支持Trim后，在删除数据时，会不向硬盘通知删除指令，只使用Volume Bitmap来记住这里的数据已经删除。Volume Bitmap只是一个磁盘快照，其建立速度比直接读写硬盘去标记删除区域要快得多。这一步就已经省下一大笔时间了。然后再是写入数据的时候，由于NAND闪存保存数据是纯粹的数字形式，因此可以直接根据Volume Bitmap的情况，向快照中已删除的区块写入新的数据，而不用花时间去擦除原本的数据。


It's no secret that many Android phones and tablets show a decrease in performance over time. Nexus devices are not immune -- it's particularly noticeable with the original Nexus 7. Our friend Brian Klug over at AnandTech discovered an interesting tidbit while testing the new and improved Nexus 7: Android 4.3 supports TRIM. What this means is that Google's mobile OS can now instruct the flash storage controller when to collect / recycle unused data pages / blocks. The net result is that devices running Android 4.3 will no longer become sluggish with time -- in fact, existing Nexus handsets and tablets will see performance improve after the update. It also looks like Jelly Bean invokes TRIM maintenance once within a 24-hour window (after one hour of inactivity), and only if the battery is 80% full (30% when charging). Follow the source link below for all the details.