Filling up the SSD with data
For obvious reasons, when an SSD is tested, the drive is
always tested as a spare drive, and is generally always empty (no data on the
drive) during the synthetic benchmarks. There is no other way of having a level
playing field for all the SSDs under test. This of course changes during the
real world tests we conduct here at Myce.com.
Real users of course don’t buy an SSD for it to remain
empty, and how full the SSD will eventually become varies from one user to the
next. What I thought would be useful is to run tests on the SSDs with real data
on the drives, and at different levels regarding how full the drive is.
For these tests the SSD is connected as a spare, and I test
at three different levels.
- Level 1: There an operating system installed on the
SSD, and all the applications that I use are also installed. In my case
that amounts to approximately 44GB of data on the SSD.
- Level 2: The SSD is filled to 60% of its formatted
- Level 3: The SSD is filled to 80% of its formatted
For the 60% and 80% tests, the type of data varies from
compressible to incompressible data, and file sizes range from a few Kilobytes
to very large files of several Gigabytes, then a single run of Anvil’s SSD
Benchmark is run (100% incompressible).
It is also worth noting that the larger capacity SSDs will
tend to slow down less than their smaller counterparts, as the larger SSDs will
have more free NAND available to work with, and this is only a quick burst test
that all members will be able to run for themselves. The real test is the Myce
Sustained Performance test, which you can find a little further down the page.
In the graph below, I present the results.
Filling up an SSD with data can certainly cause a slowdown to
occur on some SSDs. The Samsung 850 EVO mSATA 500GB SSD experienced a slight
slowdown when filled with data, but the decrease is so slight that it should go
unnoticed. The Samsung 850 EVO M.2. 250GB SSD again shows a slowdown. It’s not
a large speed decrease by any means but, according to this test, the M.2. SSD
does slow down to a greater extent than the larger capacity mSATA SSD.
This however is a short burst test and we will see what
happens in a much more gruelling test below.
Myce Sustainable Performance Test
Over the last few months I have been studying countless
analyzer traces of real computing workloads, and also developing a test that
would accurately emulate and measure how performance is sustained over a period
of time. For obvious reasons, it is not possible to test an SSD review sample
over several months before publishing a review. The solution was to condense
this down to a manageable test, that doesn’t take too long to run.
I will make it clear right from the outset that this is not
a torture test. Bringing any SSD to its knees is not helpful in the least, as I
for one would not use any SSD that had slowed down to crawl, just to prove a
point. The Myce Sustainable Performance test, I believe is a tough, but
sensible test pattern to use for measuring how an SSD will be behave once it’s pushed
hard over a period of time.
The test pattern is "workstation" based, and
closely emulates a typical video or graphics workstation environment. The
results are measured using the same hardware I use for the Myce Reality Suite
tests, however, the test data and measuring system use a different method.
From the 80% full test listed above, I already have an SSD
with a lot of data on it. Adding to the data that is already there, the
"Sustainable Performance" test data is added. This test data is
approximately 20GB is size, so once this is added the SSD is pretty full.
The test is then run for a period of 20 minutes. 60
performance measurements are taken for every minute of the test, and an average
performance figure is generated after each minute. At the end of the test I
have 20 performance measurements which are then used to generate the graph
The faster SSDs will obviously sustain more writes then the
slower SSDs. For the fastest SSD in this test, the test pattern generated 146GB
of writes, and 193GB of data was read from the SSD during the test.
When reading the graph, you should not pay too much
attention to which drive is the fastest, but instead look at the sustainable
performance curve of each SSD, as this is what this test is all about.
For the SSD that I am reviewing, I will also add a second graph
which looks at the result in more detail.
So let’s look at the results.
Detailed results for the
The Samsung 850 EVO mSATA 500GB SSD has very good
sustainable performance when pushed extremely hard. There is a slowdown, but
it’s only down by 7 MB/s from peak performance. I highly doubt anyone would be
able to notice this slowdown in the real world.
The Samsung 850 EVO M.2. 250GB SSD however has slowed down
quite a lot. With only 3GB of emulated SLC NAND, and fewer available channels
between the SSD controller and the NAND compared to the larger 500GB mSATA SSD,
the 850 EVO M.2. 250GB SSD just can’t quite keep pace with this very heavy
This concludes our review. To read the final thoughts and
conclusion, click the link below….