Given that is at exact 10 minute marks (7:30, 7:40, 7:50) I would first suspect a periodic job of some sort. An internal 10 min. timer (eg. a checkpoint interval) would run every 10 mins, but unlikely at exactly 10 minute marks. It could be either a job on the mirror, or a job on the principal that generates log that requires processing on the mirror. So first thing I would look would be SQL Agent history on both machines.

If that yields no results, capture SQL Server counters and see what correlates with the spikes.

Given that is at exact 10 minute marks (7:30, 7:40, 7:50) I would first suspect a periodic job of some sort. An internal 10 min. timer (eg. a checkpoint interval) would run every 10 mins, but unlikely at exactly 10 minute marks. It could be either a job on the mirror, or a job on the principal that generates log that requires processing on the mirror. So first thing I would look would be SQL Agent history on both machines.

If that yields no results, capture SQL Server counters and see what correlates with the spikes.

Updated

Some counters worthy of monitoring to understand the origin of the load spikes:

• Batch Requests/sec
• Logical Connections, Logins/sec, Connection resets/sec
• Write Transactions/sec, Backup/Restore Throughput/sec
• Log Bytes Received/sec, Log Bytes Sent/sec
• Active steps
• Tasks Running