i...@bsdimp.com (Warner Losh) writes: >I've not used any m.2 devices. These tests were raw dd's of 128k I/Os >with one thread of execution, so no effective queueing at all.
gossam: {4} dd if=/dev/rdk0 bs=128k of=/dev/null count=100000 100000+0 records in 100000+0 records out 13107200000 bytes transferred in 8.766 secs (1495231576 bytes/sec) That's about 50% below the nominal speed due to syscall overhead and no queuing. With bs=1024k the overhead is smaller, the device is rated at 2.5GB/s for reading. gossam: {7} dd if=/dev/rdk0 bs=1024k of=/dev/null count=10000 & 10000+0 records in 10000+0 records out 10485760000 bytes transferred in 4.371 secs (2398938458 bytes/sec) >Just ran a couple of tests and found dd of 4k blocks gave me 160MB/s, >128k blocks gave me 600MB/s, 1M blocks gave me 636MB/s. random >read/write with 64 jobs and an I/O depth of 128 with 128k random reeds >with fio gave me 3.5GB/s. This particular drive is rated at 3.6GB/s. Yes, those are similar results. With multiple dd's the numbers almost add up until the CPUs become the bottleneck. However, I was looking for devices that even fail the dd test with large buffers. Apparently there are devices where you must use concurrent I/O operations to reach their nominal speed, otherwise you only get a fraction (maybe 20-30%). -- -- Michael van Elst Internet: mlel...@serpens.de "A potential Snark may lurk in every tree."