If you are stuck using SMB1 that is definitely a problem. SMB1 sucks. On XP you couldn't get much beyond 40MB/sec without serious problems. I was able to consistently hit 120MB/sec, and somewhere here I have a screenshot copying over Gb LAN where the speed was 131MB/sec. :D
As for what you are doing wrong, I don't know. I don't use OSX (I own zero Apple devices). I'd start with using Windows 7 (or 8/8.1 with max protocol set to SMB2) to see the performance you get. If possible use an SSD on your desktop/laptop and make sure your pool can provide the throughput you want to test. If that's okay then you'd have to look at what OSX is doing wrong (or at least what isn't optimized).
Big picture, getting 5% performance gains from jumbo frames is typically exaggerating the benefits of jumbo frames. The fact that you are getting 30% (assuming you are actually getting that kind of value from jumbo frames), tells me something is off with your network, somewhere.
As for what you are doing wrong, I don't know. I don't use OSX (I own zero Apple devices). I'd start with using Windows 7 (or 8/8.1 with max protocol set to SMB2) to see the performance you get. If possible use an SSD on your desktop/laptop and make sure your pool can provide the throughput you want to test. If that's okay then you'd have to look at what OSX is doing wrong (or at least what isn't optimized).
Big picture, getting 5% performance gains from jumbo frames is typically exaggerating the benefits of jumbo frames. The fact that you are getting 30% (assuming you are actually getting that kind of value from jumbo frames), tells me something is off with your network, somewhere.