Backup to a remote server

Question

Backup

Good evening. The company is engaged in IT services. There was a question about the organization of backup for clients. The data type can be different. I would like to know about the server part. There is a server. How will it be correctly configured so that:
a) there is a secure connection during backup
b) there is confidence that in case of a failure we will get our data (be it a dead disk or some other incident)
c) because. this service will not be provided as a separate one, we would like to reduce the cost of its implementation

There was an idea to create separate ftp accounts for each organization, but there are doubts about the security of FTP itself.
With the software, the issue is more or less resolved. Either Duplicati or Cobian (if there are objections or suggestions, I'm glad to hear them)

Upd. Looked towards Amazon s3. Of course, it is a little different from the first idea. But firstly, the question of your own server disappears, and secondly, the issue of fault tolerance will be solved. Who will say about this?

Answer 1

Duplicati has support for Rackspace. Selectel has Rackspace support. With Selectel, you can open up to 10 accounts for one client (if you bring them money in interesting quantities, perhaps agree on a larger number of accounts). In the control panel, you will see in which directory how much is stored. Each account has access only to its own directory in which (and subdirectories) backups are stored. You benefit from what Selectel charges for everything stored in bulk, and you from your customers - at retail.
I don’t work in Selectel, it’s just the only convenient solution that came up to us in such a situation. Then we made our storage in the data center, and began to make copies to our servers via ssh (which is also available in Duplicati).

Answer 2

If the problem is only in ftp, then there are other protocols - for example, sftp / scp based on ssh.

Answer 3

ssh - here and sftp and scp / rsync, according to the account for the organization + encryption.

Answer 4

The question is too vague. What are the storage requirements: just drag and drop ready-made archives from the client or as separate files? Do you need the ability to restore certain files? Are the backups full or incremental? What are the volumes? Will the information be encrypted on the client side? Etc.
Based on the answers, you can suggest a lot of things: sftp, scp, rsync, obnam, Bacula, BackupPC and much, much more.