by Robert Tanner on March 18, 2013 in Solid-State Drives
Looking for a mainstream SSD but need help deciding which to choose? Is that $10 difference really worth it? Who’s got the most reliable SandForce based-SSD around? Why does Intel have so many SandForce SSDs anyway? All these questions and more are answered within!
Originally developed by Intel – and since given to the open-source community – Iometer (pronounced “eyeawmeter”, like thermometer) is one of the best storage-testing applications available, for a couple of reasons. The first, and primary, is that it’s completely customizable, and if you have a specific workload you need to test a drive with, you can easily accomplish it here. Secondly, it bypasses the Windows disk subsystem entirely, meaning it bypasses the OS drivers and writes directly to the storage media. This has important implications, such as it means Windows 7 cannot correctly align Iometer to match the SSD or HDD sector alignment.
We have updated our test suite to the latest stable 1.10 rc1 build of Iometer, which was released in December, 2010. This version makes some changes to be aware of; specifically, it gives the option for three types of data sets used during testing. 2006 and earlier versions used a pseudo-random dataset for testing, while the 1.10 build will default to a “repeating bytes” test pattern. A full random test mode was also added. To avoid giving SandForce drives an unfair advantage (they rely on data compression to achieve their performance), we will stick to the pseudo-random test pattern for all of our testing.
We have configured Iometer for correct 4KB disk alignment using a single 8GB test file from within Windows, meaning they are acting as the host OS drive with no other drives in the system. We run individual random 4KB read and write tests at a queue depth of 3 and again at 32. Then we run the 128KB sequential read & write tests using a queue depth of 1. In addition, all drives are in a dirty state prior to testing – this means results will not be comparable to advertised manufacturer results. Our goal is to measure end-user performance under real-world conditions, and so our testing reflects typical SSD performance after it has been used for some length of time in a system. Each test pattern is run for 5 minutes to achieve an average result.
In addition, we have created three Iometer disk usage scenarios that should roughly approximate database, file server, and workstation usage patterns. These scenarios are run individually for 10 minutes each within an 8GB file on the drive, which is an unusually harsh scenario for any sort of SSD. Drives that are able to offer better sustained performance over time and those that favor certain file size accesses will do well here. All three tests are configured for a queue depth of 32 to show which drives are best capable of dealing with heavy workload scenarios.
“IOPS” is simply the measure of performance relative to a certain disk access size, specifically 4KB or 512 bytes, or any size desired. Typically with SSDs when speaking about IOPS it is referred to on the assumption of 4KB accesses. With this in mind, it is easy to convert between IOPS and MB/s. Iometer provides both types of results to us and for the sake of concise graphs, brevity, and easily understandable results, we have elected to use MB/s for the 4KB and 128KB tests. For reference: IOPS = (MBps Throughput / KB per IO) * 1024 and MBps = (IOPS * KB per IO) / 1024.
In the read portion of the tests the 335 performs well, again slotting directly between both other SandForce drives, although right behind the leader as opposed to the SandForce value drive.
In the write tests things get a bit more interesting, with Intel’s drive easily outperforming both other SandForce drives. The m4 may offer better sequential performance, but for average consumer use, random 4KB performance is more important – in that respect the 335 easily trounces the m4.
As for the three usage scenarios, the Intel 335 performs well and stays in the middle of the pack with no dips or performance issues. The Intel 335 can’t compete at the high-end SSD market, but it wasn’t ever intended to do so.
Overall, the 335 180GB does well, offering well-rounded performance without any single point of weakness. Clearly, Intel has optimized the 335 firmware with the best balance between sequential reads & writes and random reads & writes without compromising any one of the four areas for the sake of better performance in the other three.