Why Smr Drives Are Bad?

The problem with SMR drives is that when you overlap the tracks like this, it means that there's no way to write to just a single track without affecting the data on nearby tracks. Writing data to an SMR drive requires that the drive scan multiple tracks at once and then rewrite them.

Are SMR drives that bad?

It can get bogged down during large writes and become very very slow, like 10MB/s on average slow. Reads are fine it is only writing that is affected. That being said, the SMR technology does make this drive one of the best for $s/TB on the market, just don't expect amazing performance from it.

Why are SMR drives slow?

As Blocks & Files notes, SMR disks are meant to store more data on a disk platter than conventional magnetic recording (CMR) disks by partially overlapping write tracks, resulting in much slower write performance than a non-SMR drive.