Why is so /dev/stl5 and /dev/stl6 slow perfomance?

[zstas]

# dd if=/dev/zero of=/dev/stl5 bs=65535
dd: writing '/dev/stl5': No space left on device
2360+0 records in
2358+1 records out
154570752 bytes (147.4MB) copied, 138.191708 seconds, 1.1MB/s


# dd if=/dev/zero of=/dev/stl6 bs=65535
dd: writing '/dev/stl6': No space left on device
3148+0 records in
3146+1 records out
206180352 bytes (196.6MB) copied, 338.649892 seconds, 594.6KB/s

# dd if=/dev/zero of=/dev/stl7 bs=65535
dd: writing '/dev/stl7': No space left on device
1265+0 records in
1263+1 records out
82833408 bytes (79.0MB) copied, 14.698679 seconds, 5.4MB/s

Why /system and /data have slow perfomance than /cache? When i reflash phone via Odin it has more perfomance for a little time.

[tom3q]

Why /system and /data have slow perfomance than /cache? When i reflash phone via Odin it has more perfomance for a little time.

STL is a part of a flash management system by Samsung called XSR. It's a sector translation layer responsible for wear levelling of flash partitions. However, the whole system uses a completely wrong design, which has serious flaws in terms of both performance and stability.

Your tests shows one of such issues, fragmentation of STL structures and nothing can be done to get around that, except getting rid of XSR completely (what is done in ROMs using my kernel).