Only supported on Linux. Note, this option may change going forward....itwillapplytoboth.Ifasecondintisspecifiedafteracomma,itwillapplytowritesonly.Inotherwords,theformatiseitherbs=read_and_writeorbs=read,write,trim.bs...=4k,8kwillthususe4kblocksforreads,8kblocksforwrites,and8kfortrims.Youcanterminatethelistwithatrailingcomma.bs...=4k,8k,wouldusethedefaultvaluefortrims..Ifyouonlywishtosetthewritesize,youcandosobypassinganemptyreadsize-bs...40Orderingdoesnotmatter.Ifthepercentageisleftblank,fiowillfillintheremainingvaluesevenly.Soabssplitoptionlikethisone:bssplit=4k