How much does insert performance matter?

I ran the insert benchmark using Innodb. The rate of rows inserted per second degraded from 20,000 to 2,000 during the test. I don't think another storage engine would do much more than 20,000 rows per second on that workload and similar hardware as much of the overhead is above the storage engine. But Innodb degrades by 10X from 20,000 to 2,000 rows per second over time. A storage engine would be 10X faster than Innodb if performance for it did not degrade.

Would 10X faster be enough to get you to switch? Do you need something that is faster for insert-only workloads or must it also be faster for updates and deletes?

Papers have been written that describe both the theory and practice of building systems that support high rates of inserts, updates and deletes. Some of this technology may eventually appear in a MySQL storage engine:

• Log-Structured Merge-Tree provides a framework for evaluating performance.  
• Bigtable describes a similar approach for avoiding random IO during updates. 
• ROSE describes how to combine these techniques with compression for modern CPUs (check out the authors)
• Graefe describes improvements that can be made for b-tree indexes