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Samsung SM951 NVMe M.2 PCIe 256GB SSD Review

By: Jon Coulter | PCIe in Storage | Posted: Jun 10, 2015 2:09 pm
TweakTown Rating: 96%Manufacturer: Samsung

Futuremark PCMark 8 Extended

 

Heavy Workload Model

 

PCMark 8's consistency test simulates an extended duration heavy workload environment. PCMark 8 has built-in, command line executed storage testing. The PCMark 8 Consistency test measures the performance consistency and the degradation tendency of a storage system.

 

The Storage test workloads are repeated. Between each repetition, the storage system is bombarded with a usage that causes degraded drive performance. In the first part of the test, the cycle continues until a steady degraded level of performance has been reached. (Steady State)

 

In the second part, the recovery of the system is tested by allowing the system to idle and measuring the performance after 5-minute long intervals. (Internal drive maintenance: Garbage Collection (GC)) The test reports the performance level at the start, the degraded steady-state, and the recovered state, as well as the number of iterations required to reach the degraded state and the recovered state.

 

We feel Futuremark's Consistency Test is the best test ever devised to show the true performance of solid-state storage in an extended duration heavy workload environment. This test takes on average 13 to 17 hours to complete, and writes somewhere between 450GB and 14,000GB of test data depending on the drive. If you want to know what an SSD's steady state performance is going to look like during a heavy workload, this test will show you.

 

Here's a breakdown of Futuremark's Consistency Test:

 

Precondition phase:

 

1. Write to the drive sequentially through up to the reported capacity with random data.

2. Write the drive through a second time (to take care of overprovisioning).

 

Degradation phase:

 

1. Run writes of random size between 8*512 and 2048*512 bytes on random offsets for 10 minutes.

2. Run performance test (one pass only).

3. Repeat 1 and 2 for 8 times, and on each pass increase the duration of random writes by 5 minutes.

 

Steady state phase:

 

1. Run writes of random size between 8*512 and 2048*512 bytes on random offsets for 50 minutes.

2. Run performance test (one pass only).

3. Repeat 1 and 2 for 5 times.

 

Recovery phase:

 

1. Idle for 5 minutes.

2. Run performance test (one pass only).

3. Repeat 1 and 2 for 5 times.

 

Storage Bandwidth

 

PCMark 8's Consistency test provides a ton of data output that we use to judge a drive's performance.

 

samsung-sm951-nvme-256gb-ssd-review_40

 

We consider steady state bandwidth (the blue bar) our test that carries the most weight in ranking a drive/arrays heavy workload performance. Performance after Garbage Collection (GC) (the orange and red bars) is what we consider the second most important consideration when ranking a drives performance. Trace based steady state testing is where true high performing SSDs are separated from the rest of the pack.

 

Intel's NVMe drives all have enterprise DNA and it comes as no surprise that they are able to outperform the both SM951 drives in a steady-state heavy workload simulation. The SM951 NVMe drive performs remarkably well, much better than the AHCI version.

 

samsung-sm951-nvme-256gb-ssd-review_41

 

We chart our test subject's storage bandwidth as reported at each of the test's 18 trace iterations. This gives us a good visual perspective of how our test subjects perform as testing progresses.

 

Total Access Time (Latency)

 

We chart the total time the disk is accessed as reported at each of the test's 18 trace iterations.

 

samsung-sm951-nvme-256gb-ssd-review_42

 

Disk Busy Time

 

Disk Busy Time is how long the disk is busy working. We chart the total time the disk is working as reported at each of the tests 18 trace iterations.

 

samsung-sm951-nvme-256gb-ssd-review_43

 

When latency is low, disk busy time is low as well.

 

Data Written

 

We measure the total amount of random data that our test drive/array is capable of writing during the degradation phases of the consistency test. Pre-conditioning data is not included in the total. The total combined time that degradation data is written to the drive/array is 470 minutes. This can be very telling. The better a drive/array can process a continuous stream of random data, the more data will be written.

 

samsung-sm951-nvme-256gb-ssd-review_44

 

Enterprise class SSD's dominate this test.

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