Poor NAS performance with Snow Leopard

Hi,
(this thread replaces a reply to an earlier thread that was old and not very relevant)

I'm have serious performance problems with NAS drives on my iMac (OSX 10.6.8 3.06GHz IC2D 4GB) and Mac Pro (10.6.8 2.8GHz IC2D 16GB). I recently replaced a WD iBook World NAS that was extremely slow with a new Seagate Blackarmor NAS 220 4TB Raid5. I thought the WD drive was failing because it was so slow. The new drive is no faster than the WD drive.

I can write to the drives at speeds I would expect (>50Mb/sec). Faster if connected
via a gigabit path. Reading from either drive is exceedingly slow. It takes me several HOURS to copy a 150MB file from either the WD or Seagate NAS to either Mac. I can copy the same file in several minutes to my windows PC over the exact same network connected to the exact same switch and router.

I believe there is some kind of a problem in the OSX tcpip software. I've found some information describing tcpip issues in OSX relating to tuning the delayed_ack setting in the tcpip configuration... for instance here:

iMac & Drobo FS NAS slow connection.. | Q8i.Org

I have tried these with no significant improvement.

Anybody have any clue what is going on? ALL my PC's have no problem getting reasonable transfer rates from these drives..

Please don't reply with posts describing how NAS drives are inherently slow and I should be using a..... This configuration would suit my needs if it worked as it should.

AND! Thanks in advance for any help,
Steve

After digging into the depths of the Seagate support website I found the problem.

It turned out to be an incompatibility with a D-Link DGS-2205 giganet switch. I replaced it with an older 10/100 switch and everything is fast. There were several mac users on the Seagate site reporting this problem. I can't for the life of me understand how an un-managed switch could cause such a problem with both NAS drives. I wish I had a good network analyzer to connect up and see what's going on.

Working is good. Thanks for reading..

sryan said:

After digging into the depths of the Seagate support website I found the problem.

It turned out to be an incompatibility with a D-Link DGS-2205 giganet switch. I replaced it with an older 10/100 switch and everything is fast. There were several mac users on the Seagate site reporting this problem. I can't for the life of me understand how an un-managed switch could cause such a problem with both NAS drives. I wish I had a good network analyzer to connect up and see what's going on.

Working is good. Thanks for reading..

Click to expand...

Interesting that the issue was specific to a switch, particularly a non-routing device like that. Something to do with the port speed sensing maybe?

Yes, that's about the only active feature of the device. However, the device is fully functional in other settings so it's not malfunctioning. A protocol analyzer might shed some light on it but I don't have one. I suppose I could try watching it from another machine on the same switch using wireshark to see if I can detect what's going wrong from a TCP point of view... I'll post back if I get around to that but It won't be for a week or two..
Thanks..