Re: Cloud backup
A solution that I implemented years ago for an SME (when the Internet was still called the Internet, before the marketing guys with a weather fixation arrived in town), worked thusly:
- Machine A is a file server where basically all the company's data is stored.
- Machine B is an off-site computer with approx five times the storage capacity of machine A. It stores versioned backups of machine A's data directory.
- A VPN server runs on machine B, to which machine A is permanently connected via ADSL (there was also the option of a radio connection--the machines are about 1 km apart at separate facilities).
- At 20 minute intervals, machine B launches rsync over ssh over the VPN and synchronises any changes since last backup. Backups are versioned at irregular intervals; e.g., there are three backups for the last hour, one every hour for the past two days (I think), one every three hours for the last week, every twelve for the month, etc., etc., and finally something like one per month after two years or some such. Only files that have actually changed are stored multiple times. Whatever hasn't changed, there's only one copy of, with multiple hard links (the data is read-only), so storage is not that much of a problem (generally, files get added and only relatively small files change frequently).
- The data directory on machine B is mounted read-only on machine A, so that access to backups is possible.
- Note that the backup is triggered from the backup machine, which has read-only access to the file server. At the same time, the file server has read-only access to the backup machine, so remote data corruption is highly unlikely.
- As machine B is a VPN host (so is machine A), backups can be accessed from any location by any client of machine B's VPN, not just from machine A.
- No third-party storage (aka "le nuage" / "die Wolke") is involved, and all comms between hosts are encrypted, giving a reasonable expectation of privacy and protection against non-targeted attacks. Not to mention that it's actually cheaper to have your own machines than pay for online storage anyway.
The cost of this solution was an inexpensive computer with a few big drives RAIDed together, plus the monthly charges for a normal ADSL connection, which copes well with the amounts of data involved. Over the years disks on both machines have failed, which was dealt with by replacing and rebuilding the RAID. Data corruption, accidental deletion of files, and machine A's location becoming inaccessible has been seen and the solution performed as expected, with complete success.
I'm not so much bragging about this (for there is nothing to brag about), as using it as an example of how successful SMEs use a bit of ingenuity to keep their business running and their costs under control.