Performances of ext4

for rotating media, figure the drive can do one fsync per rotation when writing to sequential file, for 7200 rpm drives this is ~120/sec.

if you are getting thousands of transactions/sec from a database test, you have some buffering going on, and unless that buffering is battery backed, you will loose it in power outages.

the one exception is that if you have multiple transactions going in parallel, you may be able to have different transactions complete their syncs in the same disk rotation, so you may get # threads * (rpm/60) syncs/sec.

enterprise storage arrays have large battery backed ram buffers, which do wonders for your transaction rate, up until the point where those buffers are filled (although even then they give you a benefit as multiple transactions can be batched and written at once, reducing the number of writes to the drives)