OCZ Agility 4 – 256GB 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 7 and 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 will use 4k boundaries if it can. The OCZ Agility 4 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.

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 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.

Queue depth 1

OCZ Agility 4 SSD – 4K random write (QD1)

At 152.17 MB/s the OCZ Agility 4 is showing exceptional performance at this queue depth, and is the fastest SSD in this test.

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

OCZ Agility 4 (Queue depth 4)

At a queue depth of 4, the OCZ Agility 4 performance is very strong indeed, and is just beaten by the OCZ Vertex 4.

Queue depth 32

OCZ Agility 4 (Queue depth 32)

The Agility 4 still hasn’t run out of steam, even at this very high queue depth, and finishes in third place in this test.

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

OCZ Agility 4 SSD – 4K random write (QD4 with fully random data)

The SandForce SF-2281 based SSDs pays a big penalty when having to deal with data that isn’t so easy to compress. The Everest 2 controller onboard the Agility 4 pays no such penalty, and finishes the test in second place just behind the Vertex 4.

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 for 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 result is below.

The Everest 2 controller is known to reach peak performance at very low queue depths, and the OCZ Agility 4 is no exception. Even with its slower asynchronous NAND it is still offering massive performance.

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

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

OCZ Agility 4 SSD (Queue depth 1)

This is where the slower asynchronous NAND begins to struggle a little. Performance is still good, but it’s no match for larger capacity synchronous NAND based SSDs.

Queue depth 4

OCZ Agility 4 SSD (Queue depth 4)

With a higher queue depth the Agility 4 starts to motor, but it’s still a little bit behind some of the other SSDs in this test.

Queue depth 32

OCZ Agility 4 SSD (Queue depth 32)

With a high queue depth the Agility 4 is performing extremely well, and finishes this test in third place.

4K random read queue depth profile.

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

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

If we look at the OCZ Agility 4 4K random read performance in detail, it is quite similar to the Vertex 4, albeit quite a bit slower.

IOMeter 512KB write test with repeating data.

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

OCZ Agility 4 512K Sequential write with repeating data

The OCZ Agility 4 has good sequential writing performance, but with data that is easily compressed by the SandForce based SSDs, it can’t quite keep pace with them.

IOMeter 512KB write test with fully random data.

This test is 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.

OCZ Agility 4 SSD – 512K sequential write with fully random data

With data that is not so easy to compress, the SandForce SF-2281 based SSDs take a big hit in performance, and the Agility 4 is well ahead of all the SandForce based SSDs, but is still quite a bit behind the Vertex 4.

IOMeter 512KB sequential read test QD1.

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

OCZ Agility 4 SSD – 512K sequential reading test QD1

The OCZ Agility 4 certainly struggles a bit with sequential reading at low queue depths, and is the slowest SSD in this test by quite some margin.

IOMeter 512KB sequential read test (dual threaded).

This test measures 512k sequential reading performance QD2.

OCZ Agility 4 SSD – 512K sequential reading test QD2

Once again the Agility 4 is struggling to keep pace, and the queue depth for sequential read really needs to get above a value of 4 before it starts to redeem itself.

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).

OCZ Agility 4 SSD – Workstation simulation

The workstation test pattern contains quite a bit of low queue depth sequential reading, therefore the Agility 4, while still showing good performance, can’t keep pace with quite a few of the SSDs in this test.

Summary

Overall the OCZ Agility 4 SSD has done well in the IOMeter tests. It has excellent writing performance, in fact in many cases it pushes the OCZ Vertex 4 quite close in this department. Unfortunately reading performance, especially at low queue depths is not a strong point of the Agility 4, and it will be interesting to find out if this has a large impact on performance in the real world tests that will appear later on in this article.

Now let’s head to the next page where we will look at how the OCZ Agility 4 SSD performs using a brand new benchmarking application….

 

• Synthetic benchmarks
• Anvil's Storage Utilities