Micro SD Card extension cable test. Short Vs Long Vs card slot. Raspberry Pi 400.

Turns out that SD cards can give very poor results if you have been running an OS for a while. A fresh install made all the difference.

Results
Samsung EVO 32GB (160 days ago)
Sequential write speed 24871 KB/sec (target 10000) – PASS
Random write speed 626 IOPS (target 500) – PASS
Random read speed 3513 IOPS (target 1500) – PASS

long cable
Sequential write speed 13212 KB/sec (target 10000) – PASS
Random write speed 79 IOPS (target 500) – FAIL
Random read speed 3210 IOPS (target 1500) – PASS

short cable
Sequential write speed 13204 KB/sec (target 10000) – PASS
Random write speed 78 IOPS (target 500) – FAIL
Random read speed 3380 IOPS (target 1500) – PASS

samsung 32 evo in sd slot
Sequential write speed 13162 KB/sec (target 10000) – PASS
Random write speed 78 IOPS (target 500) – FAIL
Random read speed 3349 IOPS (target 1500) – PASS
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Samsung 32 evo new install
Sequential write speed 23684 KB/sec (target 10000) – PASS
Random write speed 582 IOPS (target 500) – PASS
Random read speed 3587 IOPS (target 1500) – PASS

Samsung 32 evo new install short cable
Sequential write speed 16934 KB/sec (target 10000) – PASS
Random write speed 696 IOPS (target 500) – PASS
Random read speed 3505 IOPS (target 1500) – PASS

Samsung 32 evo new install long cable
Sequential write speed 25332 KB/sec (target 10000) – PASS
Random write speed 706 IOPS (target 500) – PASS
Random read speed 3491 IOPS (target 1500) – PASS