Peter Grandi <pg@xxxxxxxxxxxxxxxxxxxxxx> > Also, the MDRAID write journal is usually (and should be) a lot > smaller than a whole flash SSD unit, so you can use a small part > of a flash SSD for write journaling and most of it for caching. I thought journal write-back mode should use large ssd space,like bcache which will prevent random write at all cost. but reading the document again, it said "The flush conditions could be free in-kernel memory cache space is low". since the memory won't be too large compare to normal ssd disk, maybe a small optane ssd is best for mdadm write-journal.
