Mac Pro very slow with NAS (network attached storage) after OSX Update

Question

*Hello,*
**I seem to have a rather unknown problem because after hours of google'ing I found nothing.**
**I'm working on a late 2008 Mac Pro with the 8 core Nehalem processor and 12 gigs of ram and some other hardware like a Blackmagic Decklink HD extreme.**
**(If you care to know the exact specs I can gives those to you, but right now I'm degrading the Mac Pro to 10.6.0.)**
**The Mac Pro connects via an ethernet cable > ethernet breakout > directly to an Mac Pro G5 PPC on a CAT5.E ethernet cable.**
**This G5 is running leopard and has our hard drives and RAID connected to it of which we work on our Mac Pro 2008. Normally this gives us the ability to read with over 100 mb/s and write at about 70 mb/s (Blackmagic diskspeed test).**
**But recently our drives got really, really slow. It wouldn't even play PAL footage realtime in our Final Cut timeline.**
**But as we downgrade to 10.6.0 this problem is gone. So we think that when we upgrade to 10.6.5, the problem initiates.**
**How does this happen and, more importantly, how do we get rid of this?!**
**Good to know; our 27" iMac or any other device in this building _does not have_ this problem. It's just the Mac Pro after an update.**
**Please help us out.**
**Kind regards,**
*W.*

Answer 1

I have the same problem with any mac that has 10.6.  On macs that I can go back to 10.5 on they work fine and fast.  I install a used system at a client and that CPU is new enough to not be able to revert to 10.5 and their NAS is so slow that it is unless. So it's Apple's problem, they broke the protocol for NAS in 10.6 and will not fix it.  My clients don't want to make the Move to 10.7 at this time,I am not eve sure if NAS will work well with 10.7 and I think Apple has to rethink its policy of forces us to upgrade to the lastest OS to get their problems fixed.  Fix 10.6 to NAS protocol.
Maybe we don't need major system upgrades every year..  Fix the current system before you give us more problems with a major OS upgrade. 
Now I might sound tainted, but I have been an Apple person since the first, Apple II came to market.. I sold many of them.  So lets not go back to Apple 1980's when they couldn't get anything right..  They may be all powerful, now but they need to remember when there were rumors of them being sold and the stock sold for $11.00 a share.
I have searched for a fix, and many forums have stated the problem, but I just can't figure why they haven't relized that Apple mess up the protocol in 10.6.  Its simple, everything works fine on 10.5 they forced us to upgrade to 10.6 and it's broke.  go back to 10.5 and it's fixed.  So logic states that Apple's 10.6 is different when it comes to NAS protocols...  Simple...  Fix go back to 10.5  Real fix..   Apple needs to fix it with a patch to 10.6
I have no problems with someone proving me wrong that it works fine, in 10.5 and is broken, very slow in 10.6..