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
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
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
- 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 oscillating around an average of 30 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
both the burst of writes at a Queue Depth of 1 and at a Queue Depth of 32.
Now let’s head to the next page, to look at the
Conclusions from this review…..