One knob you could change that should radically alter that is zfs_txg_timeout which is how many seconds ZFS will accumulate writes before flushing them out to disk. The default is 5 seconds, but I usually increase mine to 20. When writing a lot of data, it'll get flushed to disk more often, so this timer is only for when you're writing small amounts of data like the test you just described.
> like might happen for some programs that are writing logs fairly continuously
On Linux, I think journald would be aggregating your logs from multiple services so at least you wouldn't be incurring that cost on a per-program basis. On FreeBSD with syslog we're doomed to separate log files.
> over a 10 year span that same program running continuously would result in about 100 TB of writes being done to the drive which is about a quarter of what my SSD is rated for
> like might happen for some programs that are writing logs fairly continuously
On Linux, I think journald would be aggregating your logs from multiple services so at least you wouldn't be incurring that cost on a per-program basis. On FreeBSD with syslog we're doomed to separate log files.
> over a 10 year span that same program running continuously would result in about 100 TB of writes being done to the drive which is about a quarter of what my SSD is rated for
I sure hope I've upgraded SSDs by the year 2065.