Does it mean that if I have 30TB of data, it will take 30GB of RAM just for Crashplan?
According to the Crashplan help pages:
http://support.code42.com/CrashPlan/Latest/Troubleshooting/CrashPlan_Runs_Out_Of_Memory_And_Crashes
What I do to try and get around this is create multiple backup sets. My theory is that if I can keep each backup set to around 1 TB I'll be ok. It seems to work, I've backed up 3.5 TB so far and haven't had any memory problems.
But 30 TB is a different story That would probably take a few years to backup. I'd use Crashplan for your critical data and then find some other kind of local backup for the less critical data.
Just a quick comment. The crash plan page in reference also said that it needs all that memory because of deduplication. If you are backing up a lot of AV content, you won't benefit from dedupe. I think you can even turn dedupe off for specific jobs...