Calculate the size needed for your extended datastore

The extended datastore must have enough space to contain the amount of data generated by the ExtraHop system. The following procedure explains how you can calculate approximately how much free space you need for your extended datastore.

1. Log in to the ExtraHop system through https://<extrahop-hostname-or-IP-address>.
2. Click the System Settings icon, and then click System Health.
3. Scroll down to the Data Feed section.
4. In the Metric Data Lookback Estimates chart, note the Rate and Estimated Lookback for each metric cycle (or time period) that you want to store on the external datastore. Estimates are based on metrics written during the selected time interval.
   
   

   

   
   
5. Calculate the amount of required space by applying the following formula: <rate> x <lookback_time>, and then convert the value to standard units.
   For example, in the figure above the rate for 5-minute metrics is 39.3 KB/s.

   1. Convert the rate from seconds to days: 39.3 * 60 (seconds) * 60 (minutes) * 24 (hours) * 30 (days) = 101865600 KB for 30 days of lookback.
   2. Convert the rate from kilobytes to megabytes: 101865600 / 1024 = 99478 MB for 30 days of lookback.
   3. Convert the rate from megabytes to gigabytes:99478 / 1024 = 97 GB for 30 days of lookback.

   To store all of the 5 minute metrics from this ExtraHop system for 30 days, you need 97 GB of free space.