Hi Telnet,
I invite you to read
http://community.arubanetworks.com/t5/AirWave/Airwave-Disk-Space-Usage/td-p/19484 for some more context as well.
Yes the sizing guide is a good start but I have had terrible experiences with running Airwave on an ESX server and have moved to dedicated hardware and it has been light and day.
As for HD space, the sizing guide does not take into account the number of unique clients Airwave will gather information on and by not tweeking the historical data retention section of Airwave, you can quickly run out of diskspace if you are not careful.
Here is an example of a current customer of mine:
Customer with 2200 devices
AMP Server
----------
RAM: 64 Gb of RAM
HD: 1.5 Tb RAID-10 24x146Gb 15K (more than what the recommended was)
CPU: 2 x Intel(R) Xeon(R) CPU E5-2665 0 @ 2.40GHz Hyper-Threaded 8 Cores 20480 KB cache (2400.021 MHz actual)
Performance is great with this server after some tweaks because it is monitoring 21 active Aruba controllers and > 2200 APs but what happened to me is I quickly ran out of diskspace, yes even with 1.5Tb and this was due to me not tweeking the Historical Data Retention section. Our AMP server saw anywhere from 20,000 to 25,000 daily clients therefore...since every MAC address takes up a fixed size amount of RRD space which greatly depends on how long you have set HDR for different data collection points, I would take this into account when sizing a server.
The space hungry ones are 'Client Data Retention' and 'Client Association and VPN Session History'
It is very hard to size a server when you're using an Airwave to monitor hotspots like mine but if you are monitor a campus type location with repeat client then the sizing guide does an adequate job of sizing.
For example, a financial customer of mine with 1289 devices (APs and controllers), averaging out at 1,000 clients per day. I am only using 74Gb of HD space.
The key here is to make sure you have properly tweeked your server for the needs of your network.
I hope this gives a little more insight.