OakGate Steady State Tests
Sequential Writes to Steady State
This test starts with a purge (Secure Erase), so that the
drive is in a FOB state, and then performs 128K Sequential Writes until twice the
drive’s User Capacity has been written to.
Here is a graph showing the resulting Write Bandwidth over
You can see that the Samsung 860 PRO 256GB very quickly
settles into a steady state of 523MBs, which remains remarkably consistent
throughout the test. This can be compared to the Samsung 860 EVO 250GB, whose
speed crashed to around 300 MB/s after its maximum write cache size of 12GB was
exhausted. Here’s a reminder of what the 860 EVO 250GB looked like –
So, in this test a clear victory for the Samsung 860 PRO
256GB versus the EVO 250GB with its SLC Write Cache technology (though I must
mention that the difference would be far less significant with the higher
capacity EVO drives)
4K Random Writes, FOB to Degraded (Steady State) to Recovered
This test is designed to fully degrade the drive’s
performance and then see how it recovers following a Trim and a period of Rest.
In this test I start with a purge
of the drive to take it to a FOB state.
- FOB Performance – 4K Random
I then test the FOB 4K Random
Write Performance at Queue Depths of 1 and 32, in an IO Range of 16GB, the
result was as follows –
- Sequential Writes to two times User Capacity
I then performed 128K Sequential Writes to the drive for
twice the drive’s user capacity (as in the previous Sequential Writes to Steady
- 4K Random Writes for 1 Hour
This was immediately followed by performing 4K Random Writes
to the drive for 1 hour. Here is a graph showing the resulting Bandwidth over
You can see that the Random 4K Write performance drops
significantly after around 50 seconds and the performance then settles heading
towards a Steady State of around 27 MB/s.
- Fully Degraded, 4K Random Write ‘Steady State’
I then immediately test the 4K Random Write Performance, in
an IO Range of 1GB (as we did in the initial FOB test), and the result was as
You can see that performance has dropped significantly
compared to the test performed in the FOB step. At this stage it is fair to
say that the drive’s performance is fully degraded and in a Steady State. It’s
as bad as it can get!
- Trim and Rest for 5m
I then liberally sent Sequential Trim commands to the drive
for a minute (to ensure that the drive’s entire range of logical blocks (= User
Capacity) was trimmed).
I then let the drive rest for 5 minutes before retesting 4K
Random Write performance again. The result was –
- ‘Recovered’ 4K Random Write Performance after Trim and
5 minutes rest
The outcome was –
You can see that the level of performance has improved but
it has not yet approached full recovery. This result is disappointing (as was
the result for the Samsung 860 EVO) when it is compared to the WD Blue 3D,
which had nigh-on fully recovered after 5 minutes.
Now let’s head to the next page, to look at the
Conclusions from this review…..