I'm still working on this issue, in my copious spare time.
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Haven't been able to tackle any hardware changes, but I did install ZoneAlarm on both the XP computers on the LAN. If I set the firewall to prohibit them from accessing the LAN, then the DNS-321 happily keeps on working at a decent speed.
If, however, I configure ZoneAlarm to allow them network access, my DNS-321 plummets in speed.
I wrote a little VB program that copies a 25 meg file to a directory and then reports on the speed, and it will continue to do this for specified intervals (that way I can get some work done in the intervals). Here's a report from today:
12/21/2009 1:41:42 PM 11328 kb/s n:\transfer\test.avi
12/21/2009 1:43:42 PM 12081 kb/s n:\transfer\test.avi
12/21/2009 1:45:42 PM 11990 kb/s n:\transfer\test.avi
12/21/2009 1:47:42 PM 10880 kb/s n:\transfer\test.avi
turned off XP Machine zone alarm (allowed it to communicate with LAN)
12/21/2009 1:50:33 PM 12348 kb/s n:\transfer\test.avi
12/21/2009 1:53:49 PM 330 kb/s n:\transfer\test.avi
12/21/2009 1:55:11 PM 0 kb/s n:\transfer\test.avi
12/21/2009 1:58:03 PM 279 kb/s n:\transfer\test.avi
12/21/2009 2:00:53 PM 271 kb/s n:\transfer\test.avi
12/21/2009 2:02:49 PM 0 kb/s n:\transfer\test.avi
12/21/2009 2:04:10 PM 315 kb/s n:\transfer\test.avi
12/21/2009 2:07:12 PM 225 kb/s n:\transfer\test.avi
12/21/2009 2:08:23 PM 0 kb/s n:\transfer\test.avi
12/21/2009 2:08:31 PM 0 kb/s n:\transfer\test.avi
12/21/2009 2:10:36 PM 0 kb/s n:\transfer\test.avi
12/21/2009 2:12:39 PM 311 kb/s n:\transfer\test.avi
12/21/2009 2:15:10 PM 653 kb/s n:\transfer\test.avi
12/21/2009 2:17:21 PM 518 kb/s n:\transfer\test.avi
turned on zone alarm for XP machine again
12/21/2009 2:27:33 PM 445 kb/s n:\transfer\test.avi
12/21/2009 2:29:48 PM 355 kb/s n:\transfer\test.avi
12/21/2009 2:31:59 PM 0 kb/s n:\transfer\test.avi
12/21/2009 2:33:10 PM 754 kb/s n:\transfer\test.avi
12/21/2009 2:34:47 PM 0 kb/s n:\transfer\test.avi
12/21/2009 2:37:14 PM 662 kb/s n:\transfer\test.avi
reboot NAS
12/21/2009 2:47:50 PM 8555 kb/s n:\transfer\test.avi
12/21/2009 2:49:50 PM 9280 kb/s n:\transfer\test.avi
12/21/2009 2:51:50 PM 9438 kb/s n:\transfer\test.avi
This happens for BOTH the XP machines! I've run numerous virus and mal-ware checkers on both machines, but I can't seem to WHY turning these on would affect anything.
Is there any way I can monitor what's hitting the DNS-321? Any other suggestions (short of rebuilding both machines?)