> # Data Collection

> One year’s worth of data for two variables (Rx and Tx bytes) requires a round-robin database (rrd) file size of 76 K. If errors and discards are also collected, the rrd file size becomes 110 K. The default internal values are as follows:

> - 600 samples of 5 minutes (2 days and 2 hours)
> - 700 samples of 30 minutes (12.5 days)
> - 775 samples of 2 hours (50 days)
> - 300 samples of 1 day

> A 1000-port SAN requires 110 MB for a year’s worth of historical data that includes errors and discards. If there were 20 switches in this SAN with equal distribution of fabric ports, about two to three SNMP packets per switch would be sent every 5 minutes for a total of about 100 request or response SNMP packets required to monitor the data.

> Because of their variable counter requests, flows are more difficult to predict storage space requirements for. But in general you can expect that, each extra flow adds another 76 KB.

> Note Performance Manager does not collect statistics on nonmanageable and non-MDS switches. Loop devices (FL/NL) are not collected.

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