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And even people that think they're covered sometimes turn out not to be. "But I have a NAS with two hard drives and all my files are on it. That's my backup."

And even people that think they're covered sometimes turn out not to be. "But I have a NAS with two hard drives and all my files are on it. That's my backup." "Yeah, the company that set it up did it wrong. Your files were spread across both drives, instead of copied to each drive. When one of the drives failed, all of your files went with it." "..." True story.

mnw21cam 12y ago
Repeat after me: RAID is not backup.
- thaumaturgy 12y ago
  You and I (and, hopefully, most of HN) are well aware. However, this was the very first business I had the pleasure of working with that had even attempted something resembling a comprehensive backup system, and the system they got was wrong.
- pbhjpbhj 12y ago
  RAID 1 (or say RAID 1+5) sounds like a [local] backup to me - what am I missing. Are you just saying local backup is insufficient or is it something less obvious??
  - thaumaturgy 12y ago
    RAID (of any kind) isn't a backup because it doesn't store previous versions of files. For example, if your RAID 1, 5, 6, 10, etc. array is attached as a Windows shared network drive -- which is not uncommon -- then CryptoLocker can find it, silently encrypt every single .doc, .pdf, .jpg, etc. file on it, and you're still boned because you don't have a copy of those files before they were changed. Less dramatically, sometimes people make mistakes, like editing a document, then fat-fingering a mass deletion in the document during the save process and not noticing it until a month later. Again, RAID doesn't protect you from that, but a proper backup system does. And finally, it's not unheard-of for RAID systems of any kind to just fall over. Even a RAID 10 is a whole lot of redundancy all running on a single drive controller; if that drive controller does something very silly -- and I've seen it happen, we've personally shipped systems to data recovery outfits for this -- then you can end up with garbage on all of your drives. There are two different concepts at work here. "Redundancy" and "High Availability". RAID uses redundancy, but it belongs under "High Availability" -- it's a system that's designed to still be mostly available even if it suffers a hardware failure. But strictly speaking it does not provide for redundancy of your data.
    - pbhjpbhj 12y ago
      Ha, lol, yes mirroring rather than backup. Have made the same comments as you per dropbox. Mirroring, eg RAID 1, provides some hardware redundancy; it's an entirely incomplete backup that is easily made useless. It's more like having a spare-tyre when what you really need is a spare car. Point entirely accepted but I can't help feel there is a deficiency in the language here - a hardware failover is a backup of a sort; it's not a sufficient backup to address even most potential failures.
      - thaumaturgy 12y ago
        Yeah, and ordinarily I'd happily agree with you and not take a militant "raaaaaahh that's not a backup" stance, 'cause you're right, it is a backup of sorts. Unfortunately, for a lot of people, especially computer novices, "backup" is confused with "absolute guarantee against data loss", which forces me to occasionally say things that aren't 100% true in an engineering sense. If I say, "Well, RAID is kind of a backup, but...", people seem to stop listening just before "but".
        pbhjpbhj 12y ago
        Thanks, you took the right approach!
  - wikwocket 12y ago
    RAID 1 is a very poor backup, for several reasons. For starters, anything bad that happens to one copy is likely to compromise the other copy. Deleted or corrupted the file? Oops, it was mirrored to both disks. PC stolen? Oops. Water damage in the office? Oops. Raid controller died? Oops.

mnw21cam 12y ago

Repeat after me: RAID is not backup.

thaumaturgy 12y ago
You and I (and, hopefully, most of HN) are well aware. However, this was the very first business I had the pleasure of working with that had even attempted something resembling a comprehensive backup system, and the system they got was wrong.
pbhjpbhj 12y ago
RAID 1 (or say RAID 1+5) sounds like a [local] backup to me - what am I missing. Are you just saying local backup is insufficient or is it something less obvious??
- thaumaturgy 12y ago
  RAID (of any kind) isn't a backup because it doesn't store previous versions of files. For example, if your RAID 1, 5, 6, 10, etc. array is attached as a Windows shared network drive -- which is not uncommon -- then CryptoLocker can find it, silently encrypt every single .doc, .pdf, .jpg, etc. file on it, and you're still boned because you don't have a copy of those files before they were changed. Less dramatically, sometimes people make mistakes, like editing a document, then fat-fingering a mass deletion in the document during the save process and not noticing it until a month later. Again, RAID doesn't protect you from that, but a proper backup system does. And finally, it's not unheard-of for RAID systems of any kind to just fall over. Even a RAID 10 is a whole lot of redundancy all running on a single drive controller; if that drive controller does something very silly -- and I've seen it happen, we've personally shipped systems to data recovery outfits for this -- then you can end up with garbage on all of your drives. There are two different concepts at work here. "Redundancy" and "High Availability". RAID uses redundancy, but it belongs under "High Availability" -- it's a system that's designed to still be mostly available even if it suffers a hardware failure. But strictly speaking it does not provide for redundancy of your data.
  - pbhjpbhj 12y ago
    Ha, lol, yes mirroring rather than backup. Have made the same comments as you per dropbox. Mirroring, eg RAID 1, provides some hardware redundancy; it's an entirely incomplete backup that is easily made useless. It's more like having a spare-tyre when what you really need is a spare car. Point entirely accepted but I can't help feel there is a deficiency in the language here - a hardware failover is a backup of a sort; it's not a sufficient backup to address even most potential failures.
    - thaumaturgy 12y ago
      Yeah, and ordinarily I'd happily agree with you and not take a militant "raaaaaahh that's not a backup" stance, 'cause you're right, it is a backup of sorts. Unfortunately, for a lot of people, especially computer novices, "backup" is confused with "absolute guarantee against data loss", which forces me to occasionally say things that aren't 100% true in an engineering sense. If I say, "Well, RAID is kind of a backup, but...", people seem to stop listening just before "but".
      - pbhjpbhj 12y ago
        Thanks, you took the right approach!
- wikwocket 12y ago
  RAID 1 is a very poor backup, for several reasons. For starters, anything bad that happens to one copy is likely to compromise the other copy. Deleted or corrupted the file? Oops, it was mirrored to both disks. PC stolen? Oops. Water damage in the office? Oops. Raid controller died? Oops.