more than 1GB/s write (yeah!!) but only 200-530MB/s read

[diskdiddler]

Also, a note, there is absolutely nothing, not even going all SSD, that will make your system read as fast as it writes. ZFS writes to memory and then stages it out to disk. The speed at which ZFS can write your incoming data to memory is infinitely faster than any storage device.

This is just outright untrue?

Sure for a few GB yeah it's true but once the cache is full and the machine has to commit to disk it will definitely be writing at real, not cache speeds?

All depends on quantity of memory and size of files.

 

[HoneyBadger]

This is just outright untrue?

Sure for a few GB yeah it's true but once the cache is full and the machine has to commit to disk it will definitely be writing at real, not cache speeds?

All depends on quantity of memory and size of files.

I wouldn't say "outright untrue" but rather "generalized":

Given an async write load and a system with 16G of RAM, a read of 1G would have to be served entirely from primary ARC in order to be processed and shipped out at 10Gbps. A random write of 1G will always "land entirely in RAM" and then be flushed to disk later.

If you read from records that aren't cached, any storage media activity will be slower than the call to malloc to "write into RAM"

 

[diskdiddler]

I wouldn't say "outright untrue" but rather "generalized":

Given an async write load and a system with 16G of RAM, a read of 1G would have to be served entirely from primary ARC in order to be processed and shipped out at 10Gbps. A random write of 1G will always "land entirely in RAM" and then be flushed to disk later.

If you read from records that aren't cached, any storage media activity will be slower than the call to malloc to "write into RAM"

I mean at the end of the day. If you write 600GB of data and then read 600GB you're likely to well flush out any cache on the system and be working purely with real disk and system performance.

I would expect that reads at this quantity of data, would be always faster than writes. Not by an immense margin but definitely faster.

I won't deny, occasionally I write a file to my system and I see some crazy high write performance, until the buffer fills up.