Storage options vary by plan, but on average each a user gets around 1GB of which is pooled, each site collection can use upto 50GB. The company as a whole can use upto 1TB worth. Users also get a large mailbox that can hold upto 25GB worth of mail. The user is also able to send attachments that are upto 25MB in size. Users can also opt to purchase additional SharePoint Online storage space in GB increments, charged monthly.
Students have the option for a free 25GB online storage allowance on Windows Live SkyDrive.
Backups will be something on most people’s minds in the unlikely event that all data is lost. There are data protection services provided to prevent the loss of SharePoint Online data. Backups are performed every 12 hours and held for the following 14 days.
Security components are part of SharePoint Online to help protect the environment from viruses, while also maintaining uptime and the best possible performance.