R. Stevens, in his famous book about programming in O.S. environment, taught us that when the syscall write's block size is comparable (or even equal) to the filesystem block size, the performances are the best. Lower write block size reduces performances, higher doesn't significantly increase them. This can be easily checked on "regular" filesystems, like ext2, ext3, ... on traditional spinning disks.
But it seems not to be true for solid state disks (SSD) with particular filesystem on it (in my case Apple's HFS). There's not any apparent relation between the two block sizes, and the best performances are reached far beyond the FS's blocksize; in my case FS's blocksize if 4096; best perf are reached beyond 10k of write's block size.
Is this known to be related to HFS and/or to SSD technology and how it is managed by MacOS ?