When disk drives go into error recovery, they hold the PHY connection open. The LSI 2008 SAS controllers can time out on that open connection. When the LSI controller reaches its timeout threshold, the SAS connection is reset, which causes the SAS BER error messages and event notifications.
Verify that the node firmware and drive firmware are up to date. The latest firmware packages can be downloaded from the EMC Online Support site.
If the event persists, gather logs, and then contact EMC Isilon Technical Support for additional troubleshooting. For instructions, see Gathering cluster logs.