x-25e, 25% reduction in random writes…

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%.

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3 Responses to x-25e, 25% reduction in random writes…

  1. Thats a big difference. Guess you want to make sure your REDO logs are not on the SSD. That makes LVM snapshots for backups a bit more problematic though.

  2. What filesystem are you using? Any idea if different filesystems might have different performance characteristics on the SSD w/ respect to writes?

    • matt says:

      These are ext3. Ext2/xfs have shown some promise in other tests, so I may try XFS again if I get the time…