Formatting internal MTD storage: selecting block size?
I select largest possible block size for mke2fs to avoid block fractioning as erase operation on that MTD memory performed by 16 KiB chanks:

android# /sbin/mke2fs -t ext4 -I 4096 -O ^huge_file -m 0 /dev/block/mtdblock9
mke2fs 1.41.14 (22-Dec-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
1162128 inodes, 4651520 blocks
0 blocks (0.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
142 block groups
32768 blocks per group, 32768 fragments per group
8184 inodes per group
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
        4096000

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 35 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.


then:

android# tune2fs -c 0 -i 0 /dev/block/mtdblock9
tune2fs -c 0 -i 0 /dev/block/mtdblock9
tune2fs 1.41.14 (22-Dec-2010)
Setting maximal mount count to -1
Setting interval between checks to 0 seconds


NOTE There is no need to format /data and /cache partitions. That can be done automatically in wipe data of recovery menu.