But I've heard some rumours that you could improve the network performance of the 500 by replacing come components.
This is only true if you've got very very bad network perfomance, like max 200KByte/s. When you reach ±3MB/s directly and ±1.5MB/s for the ftp-cifs roundtrip, the 3 extra capacitors will not help you. Or do you mean other components?
any reason why it does not work with helenite and works with garnet?
The cifs module in Garnet ignores the rsize and wsize setting, it always uses 4096. The new cifs in Helenite doesn't ignore these settings. The forcedirectio and wsize=8192, rsize=8192 give better performance. The reason many people had problems with Helenite is they used their old setting of wsize=16384 or heigher, because it should be better and gives better performance on other boxes, but not on the dm500. Cifs ignored it for previous images, but not anymore.
The new cifs module in Helenite should give better performance than the old one in Garnet, but only when you use the right settings. I've experimented a lot of with different settings. The settings in my previous post work best for me.
If not, you can set wsize=4096 and rsize=4096 and leave out the forcedirectio to mimic the old Garnet behaviour.
With higher wsize it seems the box takes too long to send a packet over the network and is too late to process the incoming transportstream. With higher wsize I get better raw network performance, but recording gets worse.