It seems lately there’s been an increase in posts by people disappointed because of two general misconceptions:
- Drobo will definitely increase performance compared to a single drive on the same interface (“It’s RAID so it should be faster”)
- Drobo will “save” my data from catastrophe (“If Drobo keeps my data safe, I don’t need backup”)
So I think it’s worth addressing these.
Misconception #1: Drobo will increase performance compared to a single drive on the same interface (“It’s RAID so it should be faster”)
Well, that all depends on what you’re comparing its performance to.
While increased performance is a feature of striped RAID strategies, when fault-tolerance is introduced, there is an initial performance penalty incurred to get that extra reliability.
When you write data on a non-fault-tolerant drive, you just write the data. However, when you write data on a fault-tolerant system, you must write the data, and write the extra data needed for the fault-tolerance.
This much like having two people sign your holiday cards instead of one. It adds a small bit of extra work.
Another give-and-take in performance is the fact that Drobo lets you mix drives of different makes and sizes. This is a great feature for upgrading and maximizing usable storage, but it hurts performance because different drives have different performance specs.
Back to the holiday card-signing example, this is like having multiple signers, and the different signers take a different amount of time to write their signatures. If you think of the data transfer as the speed of the “flow” of cards being signed, it can be bottlenecked by a slow signer, just like Drobo can be bottlenecked by a slow drive.
Also, because Drobo is an embedded system, its processing power is limited by the speed of its internal components. The newer Drobo S has a faster CPU, so transfers on the same interfaces compared to Drobo (non-S) are improved.
Right about now you’re probably thinking “Well, don’t enterprises use RAID for high-speed storage like with video editing and database work?” and the answer is Yes.
RAID striping does help, but it requires a large number of drives. Given the same drive parameters, an 8-drive striped array will generally outperform a 4-drive striped array, and so on.
Storage mechanisms optimized for pure speed generally sacrifice fault-tolerance, decrease storage density (less usable storage per-TB of required storage), or they involve a much larger number of striped disks in the array which then sacrifices some degree of fault tolerance, as the more drives you have, the greater the statistical likelihood of having more drives fail simultaneously.
I understand that Drobo isn’t a speed demon - if I need high-speed storage for video editing or other work, I’ll use internal drives and stripe them if necessary.
Granted, Drobo isn’t slow, especially compared to drives of a few years back. It’ll likely be faster than older drives/technology, but just keep in mind that Drobo’s secondary focus is on speed, but its primary focus is on fault-tolerance. Which leads to…
Misconception #2: Drobo will “save” my data from catastrophe (“If Drobo keeps my data safe, I don’t need backup”)
Drobo will keep your data safe from a single drive failure in standard single-disk redundancy (SDR) mode, or from two simultaneous drive failures in dual-disk redundancy (DDR) mode (Drobo-S, DroboPro, DroboElite). Unfortunately, disk failure is only one kind of catastrophe.
If lightning strikes your power line or Drobo, Drobo and its data will very likely be lost.
If the building your Drobo is in goes up in flames, Drobo and its data will very likely be lost.
If someone steals your Drobo, Drobo and its data will very likely be lost.
…and so on.
Beyond just physical catastrophes, there are a number of data catastrophes that can occur as well, that are independent of Drobo and therefore cannot be prevented by Drobo.
If your system gets a virus that deletes or corrupts files, data on your Drobo will very likely be lost.
If your operating system upgrade goes awry and it deletes the attached disks, data on your Drobo will very likely be lost.
If your cousin who’s visiting from out-of-state plugs in their USB stick and mistakenly formats the Drobo volume instead of the stick, data on your Drobo will very likely be lost.
If your nephew overwrites the business proposal you’ve been working on for two months with his online chat session log, data on your Drobo will very likely be lost.
If your dog trips over the power or data cable to your Drobo while it’s in the middle of writing something, data on your Drobo will very likely be lost.
…and so on.
How much data loss can occur, really depends on the nature of the event.
I don’t mean to panic people here, but it’s human nature to get lazy in our thoughts and actions. Drobo’s fault-tolerance is not a substitute for backup! Drobo can be part of your backup strategy, but fault-tolerance is not backup.
Another way to think of this is…
Fault-tolerance is “being careful” - Drobo is part of you being careful.
Backup, on the other hand, is insurance - insurance for those times when being careful is simply not enough.
You wouldn’t cancel your automobile insurance because you think you’re a really good driver.
You wouldn’t cancel your health insurance because you think you exercise and eat well either.
You can be the safest driver in the world, but it’s not going to stop the car that just sped through the red light from hitting you.
You could be the healthiest person of all your friends, and still drop dead at 30.
You know in the real world, there are things that happen out of your control.
And hopefully by now, you know that you need to have a backup of any of your truly-important “can’t lose” or “hate to lose” data.
This is in no way a bash or criticism of Drobo. I love my Drobo. In fact, I just got another one. Guess what for? BACKUP!!
I’m just trying to make sure people have realistic expectations and aren’t buying a Toyota and expecting it to have BMW features.
Granted, you can’t get into this forum if you’re not already a customer, but maybe the marketing folks at DRI will find a clever way to stifle some of the misconceptions in the outside world (like on the website).
EDIT 2009/12/29: Clarified point #1 so it doesn’t sound so much that Drobo is slow. Thanks for the feedback Switcher!