The iostat command has always been important to observe HDD/SDD latency numbers.
Especially SSDs are treated like magic storage devices with infinite IOPS at Planck-scale latency.
Until you discover that SSDs that can do 10GB/s don't do nearly so well (not even close) when you access them in a single thread with random IOPS, with queue depth of 1.
That's where you start down the eBPF rabbit hole with bcc/biolatency and other block device histogram tools. Further, the cache hit rate and block size behavior of the SSD/NVME drive can really affect things if, say, your autonomous vehicle logging service uses MCAP with a chunk size much smaller than a drive block... Ask me how I know