So in my previous post I showed some benchmarks showing a large drop off in performance when you fill the x-25e. I wanted to followup and say this: even if you do everything correctly ( i.e. leave 50%+ space free, disable controller cache etc ) you may still see a drop in performance if your workload is heavily write skewed. To show this I ran a 100% random read sysbench fileio test over a 12GB dataset (37.5% full ) , the tests were run back-to-back over a several hours , here is what we see:
*Note the scale is a little skewed here ( i start at 2500 reqs ).
Each data point represents 2 million IO’s, so somewhere after about 6 million IO’s we start to drop. At the end it looks like we stabilize around2900-3000 requests per second, an overall drop of about 25%.