The Two I/O Fallacies

The IOPS Fallacy

The myth:

I have more than enough IOPS to handle the workload.

The reality:

Workloads are processing 30-40% slower than they need to be due to Split, Small, Random I/O patterns generated by the Windows O/S.

Sequential I/O ALWAYS outperforms Random I/O.

The truth:

Only a small percentage of total I/O capacity is used at any one time.

We get a false sense of performance due to high IOPS and I/O Response time ratings.

V-locity optimizes the work being done, not the spare capacity that isn’t being used.

I/O Response time can be misleading

The myth:

Faster I/O response time is better.

The reality:

One individual smaller I/O transfers faster than one individual larger I/O.

This also doesn’t take into account:

Split vs. Contiguous I/O

Random vs. Sequential I/O

The truth:

The individual response time of each I/O has been overprioritized in the performance analysis equation.

Overall throughput is always slower when data is transferred with Split, Small, Random I/O.

Overall throughput is always faster when data is transferred with Contiguous, Larger, Sequential I/O.

two io fallacies small split random io to large clean contiguous io

Now that you have learned about the two I/O fallacies, at a high level, this is what we want to have happen to I/O: We take Split, Small, Random I/O and transform it into Contiguous, Larger, Sequential I/O. That’s the key to getting back 30-40% of throughput.  Your hardware SHOULD be able to perform faster, but the way Windows is handling the data logically… it’s like Windows has its foot on the brake pedal of a Maserati. Think of DymaxIO as pressing down the accelerator.