I have an HP Proliant DG380 G7 dropping one of it's arrays every hour, on the hour, for 2-5 minutes. The OS is SBS 2011 Standard, the servers runs Exchange, DC, files & Trend WFBS 8. I can watch the D Drive disappear for the duration of the problem - then it just comes back up and all is well again. There is no loss of network connectivity, although the mapped drives also disappear. We thought it might be to do with Sharepoint / VSS writers failing but it looks as though this is a symptom rather than cause. It survives a reboot. Any ideas as to what could be running on a regular schedule like this?