Sometimes on a good smartphone, the bottom line for application performance is the SD card. You can always chose from various classes of SD cards to attain required throughput, but even Class 10, sometimes, may not turn out too well.
On Android, many of us are dissapointed with SD card speeds. Even if it is Class 10 card, it performs poorly as compared to the PC.
Why SD cards are slow on Phones?
The main reason for the poor speed is the Cache size for reading from SD Card. It’s set to 128 KB, on some ROM’s even to 4 KB. You can verify the cache size on your android phone from this file: /sys/devices/virtual/bdi/179:0/read_ahead_kb
How to Increase SD card Speed
You can always edit it manually but changes are lost on every boot. In order to make changes persistent, it has to be done by loading the script on the startup through the init.d.
The easier, alternate way is to flash ClockWorkMod zip files from recovery:
Cache size: 4069. Speeds: W/s 5.6, R/s 13.7
Download zip here For Ra.1.7
Cache Size: 204. Speeds: w/s 7.9 r/s 21.7
Download Zip here For RA1.7
Other configs are also available in this post, Download
How to Choose the Right SD card Cache setting
There’s no rule of thumb here, you must find which Cache size fits best for your SD Card. For testing, use the Root Explorer to change the value, then run SD Tools Benchmark – finally flash the CWM zip file that fits your SD Card.
If you are too confused and can’t figure out whats best or too lazy, go with my suggestion of 2048 KB Cache size, which performs at best for most of the SD Cards!
That’s all for now, enjoy the improved speeds on SD card.