hello. Michael's e-mail explains the behavior I'm seeing with trying different block sizes with NetBSD and FreeBSD. The scripts below show transfers of the same number of bytes using 1m and 64k block sizes for NetBSD-9.99.77/amd64 and FreeBSD-13.1/amd64. NetBSD is using SATA3 disks with NCQ enabled and FreeBSD is using SATA3 disks with command queueing enabled. The block size doesn't change the speed of the transfers on either system. Interestingly enough, however, the FreeBSD performance is markedly worse on this test.
-thanks -Brian NetBSD-99.77/amd64 with SATA3 disk # dd if=/dev/rwd0a of=/dev/null bs=1m count=50000 50000+0 records in 50000+0 records out 52428800000 bytes transferred in 292.078 secs (179502735 bytes/sec) # dd if=/dev/rwd0a of=/dev/null bs=65536 count=800000 800000+0 records in 800000+0 records out 52428800000 bytes transferred in 292.067 secs (179509496 bytes/sec) FreeBSD-13.1/AMD64 with SATA3 disk # dd if=/dev/da4 of=/dev/null bs=1m count=50000 50000+0 records in 50000+0 records out 52428800000 bytes transferred in 322.807433 secs (162415095 bytes/sec) # dd if=/dev/da4 of=/dev/null bs=65536 count=800000 800000+0 records in 800000+0 records out 52428800000 bytes transferred in 322.433936 secs (162603232 bytes/sec)
