no..class is the write speed of microsdcard..ext is a partition of android
Well, rather say that it is partition of unix systems, but who cares.
ext2 - file system for the Linux kernel (no journal, fast but not recovery of I/O error)
ext3 - file system for the Linux kernel (journal, slower than ext2 because of journal, but provides recovery on I/O error)
ext4 - file system for the Linux kernel (journal, enhanced version of ext3)
http://en.wikipedia.org/wiki/Comparison_of_file_systems#Features
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