We have a 3 node percona xtradb cluster and two slaves attached to it. One of the slaves we want to use it for taking backups. We have GTID based replication setup between the slave and the Xtradb cluster. My question is if we are adding a new node to the xtradb cluster can we use the backups from the slave and restore on the new node. Also would we be able to avoid SST and do IST instead. I am not sure how that part works since the backups are from a slave. Any help will be appreciated.
If you are bothered by being down to essentially one node during an SST, then make it a 4-node cluster.
If you are worried about the heavy disk I/O, well, you have not avoided that -- the restore will be heavy I/O.
If you think you can always avoid SST by trying to trick it into IST, you will probably be mistaken. Galera sometimes does SST when you thing it should be able to do IST.