How does one cause a Megaraid controller to “re-scan” the devices

Thanks to Eric C. Singer for pointing me in the right direction - I've resolved this now, with much Googling. Here's what I had to do:

1. Download MegaRAID SAS VMware SMIS Provider VIB from the Support & Downloads tab on this page.
2. Enable SSH on my ESXi host. This involved the following steps:
   • Go to the Configuration tab for the host in vSphere Client
   • Select "Security Profile" under Software
   • Click the "Properties..." hyperlink next to Services
   • Click on "SSH" in the list, then "Options...", then "Start"
3. Use scp to copy the VIB file to /tmp on the host: scp vmware-esx-provider-LSIProvider.vib root@esxhostname:/tmp
4. Log into the host via SSH: ssh root@esxhostname

5. Install the VIB file: esxcli software vib install -v /tmp/vmware-esx-provider-LSIProvider.vib

   5a. If you got signature errors during the installation, install with the option --no-sig-check (official documentation states you can change the sig-check level, but i could not install regardless of the level) : esxcli software vib install --no-sig-check -v /tmp/vmware-esx-provider-LSIProvider.vib

6. Reboot the ESXi host

After the reboot, the "Host storage status" alarm fired as expected when I pulled a drive, so I'm a happy bunny :-)

For completeness, here's what I had to do to get it to send me an email when the alarm triggered:

1. Configure SMTP settings
   • Log into the vCenter Server using vSphere Client
   • From the menu, select View / Administration / Server Settings...
   • Click on "Mail" in the panel on the left
   • Enter the name of the SMTP server and sender account (this is kind of lame - would be nice if we could specify a port to connect to, SSL, authentication etc.)
   • Click OK
2. Configure the alarm to send email
   • From the menu, select View / Inventory / Hosts and Clusters
   • In the tree view on the left, click on the object where you want to configure the alarm - either at the top level (which will affect all hosts) or an individual host
   • Select the "Alarms" tab
   • At the top of the list of alarms, make sure "View: Definitions" is selected
   • Locate "Host storage status" in the list of alarms and double-click it
   • Go to the "Actions" tab
   • Add a new "Send a notification email" action
   • In the "Configuration" column next to your new action, enter the email address you need the alarm sent to
   • You probably also want to make sure "Once" is selected in each of the last 4 columns, so you'll be notified every time the status changes

As a general rule, you should never hot-swap PCI/PCI-X/PCIe cards unless they expressly state support. You can easily damage the card or motherboard by pulling or inserting the card at an angle.

That disclaimer aside, I've had luck hot-swapping NICs, as long as they weren't active (uninstalled drivers or disabled the device). I'd never dream of pulling anything that draws as much power as video, however, or something system-critical like a drive controller, without explicit support.

The trick is that you need to be able to insert or remove the card straight, to avoid shorting any of the fingers. That's most likely what happened in this case, the card was removed at an angle (as we tend to do when the machine is off), and shorted the board.

The difference between a "hot-plug" card and a non- is that the "hot-plug" cards have drivers and hardware designed to cut power on request, thus letting you safely remove the card. In the case of a NIC, disabling the device usually cuts power.