Scott Whitney wrote:
On the 10k vs 15k rpm disks, there's a _lot_ to be said about that. I don't want to start a flame war here, but 15k versus 10k rpm hard drives does NOT equivocate to a 50% increase in read/write times, to say the VERY least.
Your characterization is correct were there only the drives involved here, so no flames on your raw data.
Once you've introduced a battery-backed write cache into the mix, this whole area becomes impossible to compute that way though, and it was that context I was commenting from at least. Those are good at turning random I/O into something more like sequential, as well as reducing the number of times you pay for rotational latency in several common database operations. The effective impact is to significantly narrow the difference between drives where the seek and rotation time are the main differences in a database context--even though the worst-case IOPS doesn't really change. IOPS is an interesting number to compute, but real-world database performance isn't linearly correlated with it. Maybe if your workload consists mainly of random, uncached index scans system performance will scale just like IOPS, but that's pretty uncommon.
[Rant about making sure not to drink the storage vendor IOPS Kool-Aid deleted]
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