OakGate Sustained Writes and Recovery Tests
Sustained Sequential Writes
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
Let’s zoom in on the first 120 seconds –
You can see that the Samsung 970 EVO holds a steady speed
above 2,600 MB/s until 18 seconds has passed. This is clear evidence of the Samsung
970 EVO’s SLC Write Cache Technology being in play – as the drive is empty at
the start of the test, the drive is able to write to around a capacity of 45GB
before its SLC Write Cache is exhausted and the write speed crashes.
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 for 120 seconds 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 eventually
settles into a steady state around 140 MB/s.
- Fully Degraded, 4K Random Write ‘Steady State’
I then immediately test the 4K Random Write Performance (as
we did in the initial FOB test), and the result was as follows –
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
You can see that performance has fully recovered to support
the 20 second burst of 4K Random Writes at a Queue Depth of 1, but then the Samsung
970 EVO falls back to a somewhat degraded level of performance for the burst of
writes performed at a Queue Depth of 32. I feel that this level of recovery is
a bit disappointing.
For interest let’s have a closer look at the BW over Time,
time graph for the 120 seconds of Random 4K, Queue Depth 32 writes –
I thought we would see a period where the Samsung 970 EVO
performed at the FOB level followed by a period of significantly reduced
performance (as we saw with the Adata Sx8200). What, we actually see is a
reduced level of performance, which is largely steady throughout the period.
This can be compared to the 120 seconds of 4K, Queue Depth
32, writes in the FOB test at the start of the test –
You can see here that the peak speed was maintained through
to the end of the 120 second period.
Now let’s head to the next page, to look at the
Conclusions from this review…..