Solace uses to completely avoid disk reads on failover by synchronously keeping the hot-standby appliance in sync at all times. If you aren’t already familiar with Solace’s failover capabilities you might want to check out this post which explains Solace HA and shows some fast failovers at high message rates and this post about failover with large message spools.
The video below demonstrates a failover with over 700 GB of messages spooled across a total of more than 350 million messages. Additionally there are online clients sending persistent messages at 100K msgs/sec. With all of this message spool and live traffic, the failover time is still amazingly low.