

ENDNOTE WITH DROPBOX MAC
With the Mac Time Machine, I was able to quickly and easily revert to the file as it was immediately before my foolish careless save. I've made a mistake and saved over a file causing the loss of much work but for my backup. Having the ability to go back to a file as it was a few minutes, an hour, a day, a week, or a month ago is a really good safety net.

The cost of a 3 terabyte external drive is under US$200.
ENDNOTE WITH DROPBOX SOFTWARE
There is very good backup software built into both Windows and Mac OSs. I strongly recommend also using a separate local drive to serve as part of a backup system. Please pay attention to adamsmith's last paragraph. I pay for unlimited storage and sync my attachments to Zotero but I also have them on Dropbox for a colleague who refuses to switch to Zotero. You can set up your system to sync your Zotero library with the Zotero server and use Dropbox to store your attachments. The really nice feature of Zotero's system is that you can setup groups and share a library.

Attachment storage with Zotero can also be automatic. Storage beyond that can be purchased at reasonable rates. Zotero provides 300Mb of additional storage for attachments (PDFs, notes, etc.). The sync with the Zotero servers can be set to run automatically. The storage on the Zotero server cloud is reasonably secure unless you are working with highly sensitive encrypted stuff. There is no limit to the number of records you are allowed to store there (except the current version of Zotero doesn't run as well with umpteen records). Your data can also, at no cost, be synced with the servers at Zotero. Zotero stores your data on your local hard drive.
