On my website I have 99% reads from mysql, only few small updates/inserts but now I see that mysql have 99% writing to HD, please check this images:
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I can`t understand this, why I have up to 80MB/s writing to HD if I have only few small updates (timestamp) and few inserts?

NOTE: SDC is HD only for mysql and I using it last ~12h, before it that was SDA...