Looks interesting! I wonder whether there'd be interesting new database applications on NVMe when doing as small as 512 byte I/Os (with more efficient "IO engine" than Linux bio, that has too high CPU overhead with such small requests).
I mean, currently OLTP RDBMS engines tend to use 4k, 8k (and some) 16k block size and when doing completely random I/O (or, say traversing an index on customer_id that now needs to read random occasional customer orders across years of history). So you may end up reading 1000 x 8 kB blocks just to read 1000 x 100B order records "randomly" scattered across the table from inserts done over the years.
Optane persistent memory can do small, cache line sized I/O I understand, but that's a different topic. When being able to do random 512B I/O on "commodity" NVMe SSDs efficiently, this would open some interesting opportunities for retrieving records that are scattered "randomly" across the disks.
edit: to answer your question, I used 10 separate fio commands with numjobs=3 or 4 for each and randrepeat was set to default.
I mean, currently OLTP RDBMS engines tend to use 4k, 8k (and some) 16k block size and when doing completely random I/O (or, say traversing an index on customer_id that now needs to read random occasional customer orders across years of history). So you may end up reading 1000 x 8 kB blocks just to read 1000 x 100B order records "randomly" scattered across the table from inserts done over the years.
Optane persistent memory can do small, cache line sized I/O I understand, but that's a different topic. When being able to do random 512B I/O on "commodity" NVMe SSDs efficiently, this would open some interesting opportunities for retrieving records that are scattered "randomly" across the disks.
edit: to answer your question, I used 10 separate fio commands with numjobs=3 or 4 for each and randrepeat was set to default.