OakGate Sustained Write 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 time –
You can see that after approximately 140 seconds the write speed falls dramatically from around 520 MB/s to around 100 MB/s.
This is evidence of the SX950U’s SLC Write Cache Technology being in play. As the drive is empty at the start of the test, it is able to write to around 75 GB of data before its SLC Write Cache is exhausted and the write speed falls. It is most unlikely that the average user will ever experience such a drop in write speed.
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 Writes Bandwidth
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 Sustained Sequential Writes).
- 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 Time –
You can see that the Random 4K Write performance eventually settles into a steady state oscillating around an average of 30 MB/s.
- Fully Degraded, 4K Random Write ‘Steady State’ Performance
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 both the burst of writes at a Queue Depth of 1 and at a Queue Depth of 32. Outstanding!
Now let’s head to the next page, to look at the Conclusions from this review…..