Folks,
Here's an FYI, in case anyone else runs into this issue. And perhaps you may feel moved to contact NetApp about it as well, if your filers might be similarly affected:
Over the weekend we experienced several instances where clients (mostly NFS) were unable to transfer data to & from the filer. These outages were intermittent, but would last up to a half-hour.
To make a long story short, we traced the problem to a single NFS client running RedHat-7.3. Disconnecting the errant client from the network caused the problems to cease immediately. RedHat has released a fix, discussed at: http://rhn.redhat.com/errata/RHBA-2002-110.html
Once the immediate problem was solved (and similar client systems patched), we still were disturbed that a single buggy client (100Mbit) could take out our F820 with gigabit ethernet (there was almost no other filer activity at the time of the incidents). We entered a case with NetApp support, who directed me to their already-existing bug/RFE #72769, along with their recommendations ("fix the client"). The bug is not scheduled to be fixed.
Since we are on a mostly-open network, and since we do not control the software installed on all our client machines, we are very concerned about the potential for future denial-of-service incidents, whether accidental or deliberate. As a result, we have asked NetApp to fix the bug.
As I said, I'm mostly posting this item here so others can be on guard against the issue -- it was certainly unexpected by us.
Regards,