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100,000 erase cycles.
Simulation Tests
For purpose of testing the
effectiveness
of
wear-leveling
amongst various flash management
software, we used the following test:
1. 64MB of NAND Flash configured in
small and large block configurations.
a. Small Block - 16KB (4096 blocks)
b. Large Block - 128 KB (512 blocks)
*Large and small block NAND were
two different hardware configurations
available at the time we performed
this test. The results show that the
variance of wear-leveling can be
greater on large block, because the
wear-leveling of static data happens
less often.
2. Fill part of the volume with a
large file that is not modified. This
represents the static data on disk. For
the first series of tests, we used 10%
static data.
3. Fill remaining portion with another
file that is constantly modified. This
represents dynamic data
a. Copy data in the file
b. Delete data
c. Repeat above steps for 10,000
cycles
4. Measure the variance in the
number of erase counts for blocks on
the disk. The smaller the variance,
the more effective the wear-leveling
technique used
FlashFX Family vs. JFFS2
Results
We measure the effectiveness
of wear-leveling algorithms by
examining the erase count for each
block on the media, then comparing
the highest value to the lowest value.
We measured this in a situation
where approximately 10% of the
data on the media was static (placed
on the media and not written to again) and compared that to a situation with
approximately 60% static data.
The variance between the highest and lowest values for each test case are
shown in this table.
These graphs show the erase count all 512 flash media blocks, over a range of
4000 erase counts. JFFS2 has erase counts which vary greatly within this range,
while FlashFX Tera keeps the erase count within a range of roughly 900 erases.
These graphs show the erase count all 4096 flash media blocks, over a range of
8000 erase counts. JFFS2 has slightly better wear-leveling than on large blocks,
keeping the erase count within 2500 erases, but FlashFX Tera keeps the erases
on a narrow band of roughly 900 erases.
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