How many devices are you planning to monitor/manage using Airwave, if it is fpr 100 devices then number of cores recommended is 6 and disk space size is depend on historical retention values we set in Airwave better set to 250GB , RAM memory is more than enough.
If server is for production deployment try use Airwave ISO image to install server, OVA files is for POCs and it is optimized to monitor only 100 devices, in future if you are planning to add more devices then OVA installed server will have performances issues.