If you are creating a second partition on a phone storage card, tools such as DiskGenius can be used to try an EXT4 format with a 1024 cluster size.
When people compare EXT2, EXT3, and EXT4 for mobile use, the real differences usually come down to speed, stability, power-loss safety, flash wear, and feature set.
What separates EXT2, EXT3, and EXT4
EXT2
EXT2 is one of the standard file systems used in GNU/Linux. It is known for very good file access performance, especially with small and medium-sized files, helped by an efficient cluster cache design.
For phone use, the usual advantage of EXT2 is speed and relatively low impact on an SD card. The downside is that it does not have journaling, so it does not handle sudden power loss well. If the phone freezes and the battery has to be pulled, data inside the EXT2 partition may be lost.
EXT3
EXT3 is the next step after EXT2. It keeps the basic EXT2 format while adding journaling. It is compatible with EXT2, and converting from EXT2 to EXT3 is not difficult. In practice, EXT3 has long been considered stable and reliable.
The main benefit on a phone is better protection when the system crashes or power is cut unexpectedly. Because of journaling, it is much less fragile than EXT2 in that situation. The trade-off is extra read/write activity, which is not ideal for flash storage and may reduce card lifespan over time.
EXT4
EXT4 succeeds EXT3, but the jump is larger than the move from EXT2 to EXT3. EXT3 mainly improved journaling; EXT4 goes further by optimizing the file system’s internal data structures. It is designed to be efficient, capable, reliable, and more modern overall. EXT3 can also be converted to EXT4.
Compared with EXT3, EXT4 adds stronger features, including better handling of large files and effectively unrestricted directories. In actual use on the G6, however, EXT4 was observed to consume more power than EXT3.
A practical view for phone storage
If the second partition is being used for A2SD+, speed is not only about the file system itself. There is also the question of where dalvik-cache is stored.
With A2SD+, the command a2sd --dc2sd moves the dalvik-cache folder onto the EXT partition. There is a view that performance is better when dalvik-cache stays in the phone ROM instead. In other words, when enabling A2SD+, it may be better not to use a2sd --dc2sd, and to use only:
a2sd --enable
Is EXT2 always faster than EXT3?
A common belief is that EXT2 must be faster than EXT3 because EXT3 adds journaling overhead. That sounds reasonable, but it is not always correct.
There is also an argument that EXT3’s journaling can improve read efficiency, so EXT3 may actually outperform EXT2 in some cases. Another practical advantage is that after a system crash, EXT3 generally does not require the same kind of file system check concern associated with EXT2. Put simply, sudden shutdowns are less damaging under EXT3.
Which one makes the most sense?
The choice depends on what matters most:
- If you care most about speed and SD card longevity, EXT2 is a reasonable option, but only if you can avoid sudden power loss.
- If you want stability first while still keeping decent performance, EXT3 is the safer middle ground.
- If you want the newer format with stronger features, EXT4 is the obvious choice.
A balanced recommendation is EXT3. It offers stability, acceptable speed, and a more moderate power-use profile than EXT4, which makes it a sensible default for many phones.