Just to clarify, I wasn't suggesting SB get a bunch of NAS units. The whole conversation has centered around a single "server" machine, I was just assuming more drives in the machine to handle redundancy, as SB himself had suggested. I think when I make my 2nd blog post about my backup strategy some of my thinking on all this will become more clear. My opinion has changed a bit since my big drive failure.
Unfortunately there's no easy way around how to *fully* back up 10+TB of data, I agree. Fortunately I don't have that much data I really need to back up. It sounds like SB maybe does, so that's a conundrum. I could easily suggest a pretty reasonable backup strategy that would be "secure" and "redundant". It would just take a lot of hardware, heh. I wouldn't normally see RAID as necessary, but it might play a part solely for the simplicity it brings in addressing large contiguous disk space. Otherwise it just adds cost without really adding a worthwhile level of redundancy (IMHO, I'll just leave it at that).
As far as the idea of having to determine what's important and what's not, I think this kind of has to be a part of any backup strategy. For example some people (like myself) don't really care about backing up the whole OS, but want all the data, and that in itself is a decision about data importance that's made. Going the next step and realizing that you don't necessarily *need* triple redundancy on your archive of ripped DVD movies since you have the originals is a reasonable and important thing to do. It saves you having to back up lots of large data. I've made this call about my media archive, because I can always re-rip or re-download something. I can never re-take a photo and re-writing a document will never be the same, so that stuff is worth triple redundancy if possible.
If you really don't want to think about it and have the money and hardware space, just get 3x the number of drives you need, use basic sync/mirror for one data set, and a versioning backup program (like CrashPlan) for the other. That way you have a normal copy of the data that doesn't depend on a backup app functioning correctly (the sync/mirror) and a versioned backup that should help in the case of e.g. viruses, etc. Of course this isn't a truly bulletproof solution, first because there's no off-site backup, and second because there's only one versioned setup and if that fails and you need versioning, you may be hosed. But I consider that a pretty outside case.
Off-site backup of 10+TB of data is sadly not terribly practical. But again there are solutions to it if it's truly important. That's a situation where I really do think an external NAS-type box (but actually a locally connected one, e.g. eSATA, not network-attached) would make sense. You can get external RAID boxes that support 5 or more drives, drop 2TB units in there, and just RAID0 it so you have a big contiguous drive to back up to. RAID0 is inherently more dangerous of course, but since this is just 1 of 2 or 3 backup locations, it's ok. It's really just there for catastrophic events (e.g. your house burns down, taking your other 2 backups with it). If you have the additional drive space to do so, might as well RAID5 of course.
Note I am only suggesting RAID here because it makes it easy to address it as one big unit, not because of redundancy. I'm not sure how difficult it really is to externally address *multiple* SATA drives through eSATA, though I know it's possible (and there have been some discussions here about it). If it's possible with some of the existing external SATA drive enclosures, then it might be preferable just to have them as an additional sync target, not in a RAID but as individual drives.
Anyway, if we assume 10TB and that securely and redundantly backing up *all* of it is desired, I'd therefore suggest the following, summarized from above:
- 1 system with 10 2TB SATA drives
- An automated sync or mirroring between 1 set of 5 internal 2TB drives to the other set
- 2 external drive enclosures, one with 5x2TB drives the other with more if possible (this would be the incremental backup drive)
- Use one external enclosure in simple disk mode if possible, doing an additional sync of all drives to the external unit once a week, then take it off-site (e.g. to a storage unit, safe deposit box, etc.)
- Use the other external enclosure in RAID (RAID5 if possible) and use an incremental backup process on the internal drives targeting the external unit
This setup is pretty overkill and expensive, but will give you triple data redundancy *with* off-site backup *and* versioning. If you don't care about the off-site backup, then just remove that part from the equation and simplify.
- Oshyan
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