If you run FreeBSD under ESX (unsupported, but works) and you use a type of storage that is susceptable to slowdowns (in my case a SAN with a failed hard drive forced to do RAID5 reconstruction), you may find your FreeBSD virtual machines panic and crash.
This is caused by the SCSI disk timeout being reached on the root device. You can spot these by looking in your log for SCSI timeout messages.
To get around this, we can increase the number of retries before it fails (hopefully giving the storage device time to catch up). This is done with the following command:
You can set this to happen each boot, by editing the file /etc/sysctl.conf and adding: