Log File Size
I struggle with ROM for log file storage. It is one of those things that no one EVER looks at, but everyone covers their asses. As an example DHS requires 90 days online, 7 years offline. Anton Chuvakin from Security Warrior posted this today and I thought it was pretty good:
100,000 log messages / second x 300 bytes / log message ~ 28.6 MB
x 3600 seconds ~ 100.6 GB / hour
x 24 hours ~ 2.35 TB / day
x 365 days ~ 860.5 TB / year
x 3 years ~ 2.52 PB