Backup bogs down HA something fierce

Two physical machines in a HA cluster - each machine gets 10K+ on Passmark, and has software mirrored hard drives - running a backup to local storage bogs the whole machine down terribly - it hasn’t affected voice quality, but where I normally sit on a stand-alone machine, CPU goes to about 3% while backing up, on the cluster it is going over 25% - and the web interface is almost unresponsive - any way around this?

Perhaps a recommendation for Hardware Mirroring or SSD’s for HA?