Samsung 840 – 250GB SSD Review

I/O Performance

There is little point of having an SSD drive that has
blazing sustained reading and writing speeds, if the drive can’t handle reading
and writing of small random files. If you intend to use your new SSD drive to
store and run your operating system, then the drive must be able to cope with
the many small random files that Windows will write to the drive continually.
So I feel it is very important to test how many of these random files that a
drive can handle in one second. I believe that anything over 1,000 I/O’s per
second would be enough for most users running a consumer grade mainstream PC,
and should provide a smooth running system. But obviously, the more I/O’s that
a drive can handle, the faster the drive will feel and leave more headroom for
those huge multitasking sessions that users sometimes engage in.

The things that I will look at are the total I/O per second and
total MB/s.

Partition alignment and sector boundaries

Windows 8, Windows 7, and Windows Vista will automatically
align a partition to 4k boundaries during partition creation, Windows XP won’t.
It is imperative that an SSD’s partition is aligned. Windows XP is also
restricted to sector boundaries, while Windows 7 and 8 will use 4k boundaries
if they can. The Samsung 840 series is 4k boundary aware, and will use these
boundaries if possible. Of course it will also remap LBAs for compatibility
with the sector boundaries so that the drive can be used with Windows XP.

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IOMeter allows us to set the sector boundaries for
conducting the tests, and I have therefore set the sector boundaries at 4K,
which means the IOMeter tests are valid for Windows 7, Windows 8 and Windows
Vista users. XP users will not be able to obtain such results.

I will provide a screenshot of the tests on the review drive
for those of you who like to see the actual test result. All the comparison
drive results are represented in the form of graphs.

If any of you would like to see a screenshot from any
IOMeter test on a particular drive, please feel free to request one, and I’ll
post the screenshot in the forum thread.

All the IOMeter tests create a 10GB data set on the target
drive, and each test is run for a duration of 3 minutes.


IOMeter 4K random write test with repeating data.

The first test involves creating continual 4KB random files
on the target drive with IOMeter. I use a 4KB file size, as it is believed that
Windows will create and modify many of this size of file constantly in the
background during a typical Windows session. It is said that most 4K random
writes take place at a queue depth of only one, and I have been requested to
include this test in my reviews.

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Queue depth 1

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 4K random write (QD 1)

Samsung 840 - 250GB SSD Review

At 122.95 MB/s the Samsung 840 is performing extremely well,
and finishes this test in sixth place.

Our next test involves creating continual 4KB random files
on the target drive with IOMeter. I use a 4KB file size, as it is believed that
Windows will create and modify many of this size of file constantly in the
background during a typical Windows session. I will use queue depths of 4 and
32 for these tests.

Queue depth 4

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD (QD 4)

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Samsung 840 - 250GB SSD Review

At a queue depth of 4, the Samsung 840 delivers very good
performance, and finishes this test in seventh place.

Queue depth 32

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD (QD 32)

Samsung 840 - 250GB SSD Review

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The Samsung 840 starts to run out of steam at high depths,
and can’t keep pace with many of the other SSDs in this test. Having said that,
it’s still well ahead of the older Samsung 830 SSD, and the Crucial M4.


IOMeter 4K random write test with fully random data.

This test is exactly the same as the test above except that
the test data is fully random and is therefore much more difficult to compress.
This test was requested as SandForce based SSDs gain a lot of performance by
being able to compress data on the fly. While the above test shows the
SandForce based SSDs in a best case scenario, the following test will show the
SandForce based SSDs in a much more realistic scenario.

Queue depth 4 with fully random data

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 4K random write (QD 4 with fully random data)

Samsung 840 - 250GB SSD Review

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The Samsung 840 pays no penalty when writing data which is incompressible,
and with 253.91 MB/s it finishes the test in sixth place.


4K random write queue depth profile

For this test I used various queue depths from 1 – 32 to
give you an idea how this SSD performs at different queue depths. For a normal
desktop user, with lightweight multitasking, the queue depth will rarely rise
above 2. For heavy multitasking, the queue depth is unlikely to rise above a
value of 8.

The results are shown below.

Samsung 840 - 250GB SSD Review

As we can see, the Samsung 840 scales well to a queue depth
of three, but there is no more scaling after that. However, this should not be
a problem for a normal consumer grade workload, where queue depths are fairly
low.

Below I present a table of the results in more detail.

Samsung 840 - 250GB SSD Review


IOMeter 4K random read test.

If there are many 4k files created, then that must also mean
that many 4k files need to be read. This test measures 4k reading performance.

It is said that most 4K random reads take place at a queue
depth of only one, and readers have requested that I include this test in my
reviews.

Queue depth 1

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 4K random read (QD 1)

Samsung 840 - 250GB SSD Review

The Samsung 840 is showing very good performance at this
queue depth, and is the sixth fastest SSD in this test.

Queue depth 4

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 4K random read (QD 4)

Samsung 840 - 250GB SSD Review

Once again the Samsung 840 is showing excellent performance
at a queue depth of four, and is the fifth fastest SSD in this test.

Queue depth 32

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – random read (Queue depth 32)

Samsung 840 - 250GB SSD Review

The Samsung 840 is again performing extremely well in this
test, and finishes in third place.

4K random read queue depth profile.

This test shows how the review drive scales with increasing
queue depths.

Samsung 840 - 250GB SSD Review

Below I present a table of the results in more detail.

Samsung 840 - 250GB SSD Review

If we look at the Samsung 840 4K random read performance in
detail, we can see that it scales exceptionally well with increasing queue
depths.


IOMeter 512KB write test with repeating data.

Sequential writing performance is also very important; in
this test sequential writing performance is measured.

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 512K Sequential write with repeating data

Samsung 840 - 250GB SSD Review

TLC NAND takes longer to erase than conventional MLC NAND,
and sequential writing performance is certainly not a strong point of the
Samsung 840.

512K sequential write – Queue depth profile

While most sequential writes will rarely rise above a queue
depth of two, it has been noted from SATA analyzer traces that with more
demanding tasks, queue depths can rise very close to a queue depth of four.
This is why I now include queue depth profiles for sequential read and write.

Please note that in the following graph, I do not have the
lowest possible score set at zero. This is purely to allow the graphs to be
easier to read, but starting with a lowest possible score other than zero,
gives the impression that there are large differences between competing SSDs with
regard to performance, so please keep this in mind.  

Samsung 840 - 250GB SSD Review
512K sequential write – Queue depth profile

Below I present a table of the results in more detail.

Samsung 840 - 250GB SSD Review

The Samsung 840 reaches peak performance at a queue depth of
four, but is only marginally faster than at a queue depth of one.

IOMeter 512KB sequential write test with fully random data.

This test is almost exactly the same as the test above
except that the test data is fully random in nature. This test was requested as
SandForce based SSDs gain a lot of performance by being able to compress data
on the fly. While the above test shows the SandForce based SSDs in a best case
scenario, the following test will show the SandForce based SSDs in a more
realistic light. In the real world, the data is neither 100% incompressible nor
100% compressible, it is somewhere in between. So please keep this in mind.

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 512K sequential write with fully random data

Samsung 840 - 250GB SSD Review

With data that is not so easy to compress, the SandForce SF-2281
based SSDs take a big hit in performance. This does allow the Samsung 840 to
pull ahead of the SandForce based Sandisk Extreme, and closer to the other
larger capacity SandForce based SSDs.


IOMeter 512KB sequential read test QD1.

This test measures 512k sequential reading performance at
very low queue depths.

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 512K sequential reading test (QD 1)

Samsung 840 - 250GB SSD Review

The Samsung 840 250GB SSD has outstanding sequential reading
performance at very low queue depths, and is the second fastest SSD in this
test.

IOMeter 512KB sequential read test (dual threaded).

This test measures 512k sequential reading performance QD2.

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – 512K sequential reading test (QD 2)

Samsung 840 - 250GB SSD Review

At a more realistic queue depth the Samsung 840 250GB is still
showing outstanding sequential reading performance, and finishes this test in
first place.

512K sequential read – Queue depth profile

While most sequential reads will rarely rise above a queue
depth of two, it has been noted from SATA analyzer traces that with more
demanding tasks, queue depths can rise very close to a queue depth of four.
This is why I now include queue depth profiles for sequential read and write.

Please note that in the following graph, I do not have the
lowest possible score set at zero. This is purely to allow the graphs to be
easier to read, but starting with a lowest possible score other than zero,
gives the impression that there are large differences between competing SSDs with
regard to performance, so please keep this in mind. 

Samsung 840 - 250GB SSD Review
512K sequential read – Queue depth profile

Below I present a table of the results in more detail.

Samsung 840 - 250GB SSD Review

The Samsung 840 is a very strong performer at very low queue
depths, where it is the second fastest SSD at a queue depth of one in this
test. However as queue depths rise it still manages to be the fastest SSD, and
knocking right on the door of SATA3 maximum bandwidth.


IOMeter Workstation simulation (outstanding I/Os = 64).

When running applications you will find that there is a
mixture of small random files, and larger sequential files, being created and
read. Not only that, it isn’t just one file at a time. In this test I measure a
simulated workstation pattern, with a queue depth of 64 (threaded).

Samsung 840 - 250GB SSD Review
Samsung 840 250GB SSD – Workstation simulation

Samsung 840 - 250GB SSD Review

The Samsung 840 250GB SSD hasn’t done so well in the
workstation simulation, and is the slowest SSD in this test.


Summary

There is no doubt about it, the Samsung 840 has extremely impressive
reading performance. It has excellent small file random reading performance at
very low queue depths, and doesn’t run out of steam when the workload is
increased. Sequential reading performance is also impressive, as is small
random file writing performance. Sequential writing performance is however a
little disappointing.

Now let’s head to the next page where we will look at how
the Samsung 840 SSD performs using a brand new benchmarking application….

 

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