What is the metric "Top InnoDB I/O Data Reads"?


We’ve just started using PMM2 (yes yes, we took a long time to upgrade from version 1!!).

The metrics seem to be color coded - green, yellow, and red - which I assume means the values are within specific ranges. But I can’t always tell what the thresholds are or what they mean.

Can anyone help me understand what " “Top InnoDB I/O Data Reads” is ? And in general I’m not clear what the “Top” metrics mean - Top of what? =)

Thanks !


Hi @Aaron_Ross welcome to the Percona forums!

In general you’ll find that the MySQL Instances Overview dashboard is going to look in detail at just a subset of your environment, that is, the Top 5 graphs will select only 5 services, and the Top graphs will be the 1 highest instance.

In the case of Top InnoDB I/O Data Reads, this is the formula:
reads / (reads + writes + fsyncs)
It tells us what percentage of InnoDB disk activity is based on reads.

The colour coding is based on green up to 60%, then orange and red above this. Here is the configuration block from the graph definition:

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Thanks! very helpful.

Am I missing where the name of top service that’s selected is displayed ?

I’m not sure how to interpret those thresholds for reads - why would a high number of reads be “red” ? or am I just reading to much into the coloring ?

Thanks again.


Hi @Aaron_Ross

  1. You’re right, it doesn’t say which node is the TOP node. Personally I would look at these metric points as “informative” in order to let me dig in further. Specifically, if I have a node in 100% TOP InnoDB Writes, then I am sure I could identify that node in TOP 5 graph for InnoDB Writes.
  2. Thresholds - yes they are arbitrary, and I agree with you, the colours don’t necessarily map to anything “good” or “bad”. Like a 100% read-only node isn’t bad - so 100% shouldn’t be red…

Do you have suggestions on what colours/thresholds we should use?

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Cool - thanks.

I agree it’s easy to find the node once you understand - but if there was a way to label the graph, would be nice. =)

For the colors - I think I’d just put them on fewer graphs. We’re so trained to see green as good and red as bad!

Thanks again.


These seem like reasonable feature requests - remove the colour-coding when there isn’t a clear benefit / detrimental effect due to the value of the variable displayed. I’ll pass that on to the Engineering team - thanks for the suggestion, @Aaron_Ross !

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