hesela.devSD speed class
An SD speed class specifies a minimum sequential-access performance level under the access rules and operating conditions of its class family.
C, U, V and E marks describe performance classes, while UHS-I, UHS-II and SD Express describe interfaces. Match the host's class family and required level: equal numeric throughput in different families does not establish equivalent host support [1].
E150, E300, E450 and E600 specify 150, 300, 450 and 600 MB/s minimum read/write performance under SD Express Speed Class conditions. These conditions include host access rules and power and thermal management, rather than a promise for arbitrary workloads [2].