IOMeter v2006.07.27 – IOps

Iometer is an I/O subsystem measurement and characterization tool for single and clustered systems. It was originally developed by the Intel Corporation and announced at the Intel Developers Forum (IDF) on February 17, 1998 – since then it got wide spread within the industry.

Meanwhile Intel has discontinued to work on Iometer and it was given to the Open Source Development Lab (OSDL). In November 2001, a project was registered at and an initial drop was provided. Since the relaunch in February 2003, the project is driven by an international group of individuals who are continuesly improving, porting and extend the product.

Light desktop usage sees QD figures between 1 and 4. Heavy / power user loads run at 8 and higher. Most SSD's are not capable of effectively handling anything higher than QD=32, which explains the plateaus.

Regarding why we use this test as opposed to single-tasker tests like 4KB random reads or 4KB random writes, well, computers are just not single taskers. Writes take place at the same time as reads. We call this mixed-mode testing, and while a given SSD comes with side-of-box specs that boast what it can do while being a uni-tasker, the tests above tend to paint a very different picture.

While the 840 Pro did great with this workload (as do most modern SSDs), this is the exact worst case scenario for a first generation TLC-based SSD. The added overhead of writing with 200% greater voltage accuracy per cell means that in every test save Web Server (which is read-only), even a small fraction of mixed writes is enough to collectively drop the IOPS figures well below that of all competing drives presented here. While these are not horrible numbers, they do regress back to the X25-M days, roughly representing the mixed-mode performance of SSDs from 2-3 years ago.

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