Definition: "A Backup Plan"

zamboni wrote:
I am very tired of "hard-core-enthusiasts" constantly re-proclaiming "a NAS is *not* a backup solution". REALLY? What is the definition, then, of a backup (aside from "a second copy")??? a) I have my critical data on my PC b) I store my data elsewhere, IN CASE MY PC DIES >> In other words, my data is arranged such that it can survive a hard drive failure. Pure and simple.

I don't like it when someone says something like "a NAS is *not* a backup solution" without qualifying that statement. If data is stored primarily on another device, then a backup copy stored on the NAS is a backup. However if the data is primarily stored on the ReadyNAS, then you need to make a copy some place else for it to be backed up. So, a backup is a second copy of your data stored on a separate device. Preferably a backup solution will involve keeping copies of all critical files in multiple locations (i.e. at least one backup copy off-site) at all times.

zamboni wrote:

Lets expand on this: I have spent numerous hours (hundreds!) converting my CD collection to 320-bit MP3, and DVDs to DIVX MP4. I can replace the files, but my time was valuable. My photos, more valuable, are on my PC, my wife's laptop, AND the ReadyNAS server. However, if a single drive dies - I replace it. I have not lost data. That is a backup. Lightning struck (one drive died), I survived (I had RAID). I am absolutely OFFENDED by all the "puritans" that say a RAID is not a backup. A backup is meant to survive a single point of failure.

The RAID is not the backup in itself. Redundancy and backup can easily be confused for being the same thing. Redundancy or high-availability refers to a single component failing in a system but the system remains online. For example you could have e.g. a hard disk, power supply (if you have a dual power supply NAS) etc. fail but the system remains online.

A backup on the other hand is stored on a separate device to the primary copy. It tends not to provide immediate failover and generally needs to be restored manually. This protects you against things like accidental file deletion, file corruption etc. A backup also tends not to be entirely up to date. It could be a day old perhaps or longer depending on your backup schedule.

Also take a look at Preventing Catastrophic Data Loss. It's a very useful article to read. One common misconception is that often users think that they can pull a drive from a RAID-1 array and treat this as if it were a backup!

zamboni wrote:
OK, if a meteor strikes my house, I lose my data. However, my data is on my PC, my laptop and my RAID-5 server. In a meteor (or fire), ALL ARE LOST - despite 3 copies of my data. Same with theft, flood, etc - since shiny computer-things are attractive stealing stuff.

That's correct. That's why some go so far as to say a backup is a copy of your data stored at a separate location (i.e. off-site) to the primary copy.

zamboni wrote:
Therefore, RAID-5 *AND* backup only protects against... hard drive failure. Since, backing up your drive to an external **IS** considered a backup -- then, backing up your data to a RAID-5 array is **BETTER** than a backup.

Yes. Having redundancy on your backup is better than simply backing up to a USB drive.

zamboni wrote:
(no, I care not about "accidentally deleting stuff" -- we have "recycle bins" and "Norton Recovery" stuff, so irrelevant).

There's still the possibility your memory module fails and you get data corruption. Or you try a beta firmware and things really get mucked up badly (I don't know of any cases of this, but it's possible). Things can go wrong when data is stored on a single device. Unlikely but it's still a possibility.

zamboni wrote:
RAID-5 is a backup. Not meteor proof, but reliable.

Redundancy isn't the same as a backup. It's good, but it's no replacement for a backup. If you backup the data from your PC to a NAS, then your data is backed up, no matter whether you're using a striped RAID-0 volume (large risk you'll lose your backups) or RAID-5 or RAID-6.

Most businesses store there data on a RAID array and they realise that simply storing the data on the server does not mean it's backed up. They may not know that the server uses RAID, but even if they do, their IT advisor should be able to explain this to them and explain why backups are important.

zamboni wrote:
End or argument.

RAID (Redundant Array of Independent/Inexpensive Disks) by definition is talking about redundancy not backups. It is not designed to backup your data. Having multiple copies of your data on a single device is redundancy, not a backup. Storing data on multiple devices is a backup.

An individual has to decide for themselves what their aversion to risk is and how they should backup their data. For those with huge amounts of data it may be impractical or not feasible to backup all data. However irreplaceable data should be backed up both on-site and off-site. Some other data you may just have on-site backups of (if not concerned about losing data due to fire, theft etc.). Still other data you may just store on a RAID array (e.g. NAS) - typically this would be data, that may be able to be recreated/reobtained or is too expensive to backup (huge amount of media files). Data of even lesser importance may be stored on a single hard disk and not backed up.

On rare occasions it can be useful to deal with a problem by doing a factory default (wipes all data on NAS). It can also be an important performance troubleshooting step. So sometimes someone can ask if you have a good backup before suggesting a factory default be tried.

End of argument.