RAID is high availability, not a backup ! Let's get back to basics : reasons to backup
- HW failure - component (DD, power supply, etc...)
- HW failure - external reasons (thunderstorm, floods, fire, 2012 end of world)
- Theft
- SW failure - corruption due to bugs in a program, or subtle incompatibilities between two programs
- Human error - deletion of the wrong folder (or copy over)
- Bit rot. That is a single bit changing state within a file. That single bit can end up being unnoticeable at best, and make a file unplayable at worst. Occurrences are few and far between, but exist nevertheless.
Most of the backup methods I saw in this thread do not mention and do not address bit rot. Bit rot is not an issue if your file system is some kind of RAID and you regularly scrub the whole array. I do not use RAID, as I think the benefits do not balance with the inconveniences in the case of media files (written once, mostly read) in a home environment.
Now let's address priorities, in decreasing order.
- Home photos and videos. Those instants occurred once and are truly irreplaceable
- Personal data
- Music
- Commercial videos and movies
The first 3 items (photos, data and music) fortunately fit in a single external drive, nowadays cheaply found up to 3TB.
Here is how I proceed for all
but video.
My main PC is where I rip and do most chores.
The cleaned up files are then copied to a NAS, serving all the PCs and media sinks (XBOX, PS3, Tablets, HTPCs) in the house. That NAS (a Synology 2-disk low power box) is on 24/365 and always available to every device in the home.
I use SyncToy (free from Microsoft) in Contribute mode to copy new stuff from the NAS to the external backup drive. Here's SyncToy definition of Contribute: "
New and updated files are copied left to right. Renames on the left are repeated on the right. No deletions".
If I need to delete from the backup, I do it manually on both external (mostly off-line) backup drives.
I also copy those files to a small area within the video server (see below).
I have two backup drives, one at home and the other at work. Once in a while (depends on amount of churn) I bring the home backup to work and come back with the other to be refreshed. The drive at home is totally disconnected (power and data)
except when doing actual backup work.
Now video is simply too big to be backed up !While I cannot completely prevent fire or theft (collection is insured though), I can improve reliability and resiliency.
I rip my DVDs and Blu-rays lock, stock and barrel to ISO files stored in a dedicated "video" file server. That big box is mostly off, but I can turn it on and off remotely (Wake On LAN) usually just to watch a movie. It can hold 20+1 disks and currently holds 8 disks.
As I mentioned earlier, I do not believe in RAID for media files, but I use a form of off-line protection called SnapRAID (
http://snapraid.sourceforge.net/). SnapRAID is free. It uses dedicated parity drives (1 or 2) to build enough redundancy information to survive loss of one or two disks (any one).
Think of it as similar to RAID5 or RAID6, but on demand. A big difference however is that data disks are "vanilla", readable on any PC, contrarily to RAID5 solutions where losing 2 disks means ALL data is lost (3 for RAID6).
A side benefit of an off-line parity protection is that all but the active disk can be spun down, allowing cooler operation, contrarily to most forms of RAID protection
It is an off-line protection in the sense that I have to manually run a Sync operation after I add files to the server in order to have them protected. I run an overnight Check operation (validating the whole array, including bit rot) weekly. If a problem is found, I can run a Fix operation, to bring the array to the same state it was at the last Sync (after swapping in a replacement disk if needed).
I regularly copy the NAS content to the video server, in order to benefit from SnapRAID's bit rot protection. If a Check operation flagged a problem within those files, I could run a Fix operation then copy back to the NAS the clean files.
Finally, I closely watch the SMART attributes of the disks in the array. This can flag a developing problem
before an error occurs.
Now, all this is convenient for me, but if you do not rip movies and do not have a big box server, I think that you still need to protect yourself against bit rot. A relatively cheap insurance would be to buy one or two big disks and use SnapRAID locally, within your main PC.
Also keep in mind that off-site backup is a must (when feasible) !
Voilą, that's how I address the backup problem
Rudy
