If you have the raw data in HDFS (which most do, and which you should!), the most straightforward way to have a hot-warm disaster recovery setup is to use our Backup and Disaster Recovery tool. It allows you to set up regular incremental updates between two clusters. You then have the option of using MapReduce Indexer or Spark Indexer to regularly index the raw data in your recovery cluster and append to a running Solr service in that same recovery cluster. This way you can easily switch over from one Solr service to the backup Solr service if you experience downtime in the original cluster.
The lag would be depending on the network between the clusters and how frequent you transfer data between the clusters. To some extent it would also depend on how long time you need (i.e. how much resources you have available) to complete the MapReduce or Spark indexing workload and append it (using the Cloudera Search GoLive feature) into Solr active indexes on the recovery site.
Read on for several options.