> Suddenly instead of loading a billion rows and averaging the value in one column, you're just accesing the column itself to answer the question. From an IO perspective that's a huge savings.
The other side of this is that writing out data in that form would naively be an iop per sample, as you're usually appending one sample to 100s of time series in one request.
A significant part of monitoring TSDB design is buffering up samples and batching writes in order reduce that iop rate to something sane.
For example in the right circumstances the 1.x Prometheus design can ingest 250k samples/s on a hard disk which provides ~100 iops/s.
The other side of this is that writing out data in that form would naively be an iop per sample, as you're usually appending one sample to 100s of time series in one request.
A significant part of monitoring TSDB design is buffering up samples and batching writes in order reduce that iop rate to something sane.
For example in the right circumstances the 1.x Prometheus design can ingest 250k samples/s on a hard disk which provides ~100 iops/s.