ベン・ギルド (Ben Guild)

What is a “Drobo?” Find out how to store massive amounts of data on spare HDDs.

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Data backup can be annoying. To be truly “backed up,” you need to have multiple copies of your data: in multiple locations, and on multiple mediums. Seriously. Because, this way, if one place burns down or gets flooded, or if you suffer a catastrophic device failure, you're still protected at multiple levels in the worst case… hopefully!

I have seen so many people lose the single HDD (hard-disk drive) in their computer. Often times, it'd have had all of their family photographs on it, music collection, and more. Afterward, they're lucky to get anything back from an expensive data recovery service. Or, another horror story is when a student loses all of his or her homework assignments when a computer slides off of their bed and onto the floor. — Data-loss can be a nightmare… but in real life!

Luckily, nowadays there are services like Backblaze that offer a backup “in the cloud,” but as previously mentioned, to be truly “backed up,” you cannot rely only on a single medium.

Apple has a great built-in local service called Time Machine on Mac OS X that creates timely archives of your data whenever an external HDD is connected. However, most people don't set this up, it's not expandable to become redundant across multiple HDDs dynamically, and then if that single extra HDD fails… you've then lost your only backup!

Even if you have Backblaze, what is a great, overall local solution?

Hello, Drobo!

I bought a Drobo S, which has 5 HDD bays for pooled data storage and redundancy. For each of these bays, I have inserted a 1TB HDD. — I keep it stationary at home while I travel, containing an archive of adventures past… including music, videos, photos, old source-code, …things like that! Stuff that I don't need to carry around, but would like to retain access to later on.

I have alternate backups of this data, but Drobo provides a single, expandable, centralized volume that I can easily read from and search. If the Drobo fails, I still have another backup elsewhere, so that's cool. — See beginning of this article for the reason why additional redundancy is a must! 😃

My Drobo setup… connected to an APC UPS for AC battery backup. (There's a 5th HDD bay and light near the top of this Drobo, but it's cut off by the top of the photograph.)
My Drobo setup… connected to an APC UPS for AC battery backup. (There's a 5th HDD bay and light near the top of this Drobo, but it's cut off by the top of the photograph.)

Why Drobo?

There are other RAID solutions, but Drobo is one of the most user-friendly choices in terms of hardware.

I needed something centralized and searchable, where I could put a second copy of data. I have additional copies in other places, but this is great since it's simultaneously expandable with ease.

The Drobo is not serving as a primary backup of anything. It's only a copy. The reasons for this are rooted in the fact that devices can fail from time-to-time, as stated in the beginning of this post. You should never only have a single backup of your data! 😄

The Drobo is excellent for this, and I like it. It's so simple to maintain that I can even just leave it at my parents' house, and they can replace the HDDs if they fail … without needing my help. My father recently did this twice for me, which was cool. If one or more of the Drobo's external lights turns yellow or red, you know right away that you need to change at least one of the HDDs out!

Because the HDDs can be replaced at any time (without having to power-down the unit or take it apart) … you can literally just “hot swap” them. This trick can also be used to increase the overall storage limit, too. Here's a Vine video of me replacing a HDD with a larger one to add additional storage:

Drobo devices are definitely very interesting to look at, not to mention being incredibly useful!


As mentioned, there's always the chance that the entire Drobo device could fail or become corrupt at once, but then again, so could your computer or any other device for that matter. What's worse though, since Drobo units generally utilize a proprietary filesystem (at least at this time of writing)… you're pretty much screwed if this does indeed happen to you, since the HDDs themselves cannot be accessed directly on their own. 😔

The Drobo S does offer two features in particular that did make me more comfortable overall, though. One of them is “dual-disk redundancy,” meaning that if you do have a HDD completely fail or start to display warning signs, you're only screwed if a second and third HDD also fails before you can replace the first one and have it rebuild from the stripes across the others. This is great, and also unlikely to ever be necessary, as well… I hope!

The other feature that I really like is that it constantly scans and scrubs over the HDDs for errors. This actually leads to faster HDD failures (I guess that's a good thing, in this case? 😅) compared to most other RAID systems, but also somewhat guarantees that the device is not relying on a failing or already failed HDD without reporting or noticing it. Ordinary RAID systems generally have catastrophic failures because they do not do anything like this unless you're constantly reading across all of the data in all locations on a regular basis, and therefore when a single HDD begins to fail and the RAID enters a “degraded” state, it then finally notices the other failing HDDs only when it starts to try to recover parts of the array that are unfortunately perhaps lost forever due to unrecognized degradation from lack of use. Scary! See the beginning of the article for reasons why additional redundancy is always a must. 😅

One serious design flaw with Drobo's software

This kind of sucks: When you first setup your Drobo, you must choose the “size” of your Drobo volume.

In other words, when you connect the Drobo to your computer, even if you only have a single 1TB HDD in it… your HDD will appear as “4TB” if you choose to specify a “4TB” volume size. It's voluntary. The maximum size that you can choose for this model at this time of writing is 16TB:

Drobo “volume size” chooser
Drobo's “volume size” chooser

This situation only really becomes a problem if you try to copy too much data onto your Drobo. — The Drobo Dashboard software can alert you to the Drobo unit approaching becoming too full, but if you then continue to fill it up (or, for example, an automated copying/backup utility does this for you without you noticing since it thinks that the volume is large enough to fit more data than it actually is)… it can become corrupted and the data will be irrecoverable!! Other users have reported that by putting too much data onto the unit (even accidentally)… it actually destroys the Drobo's disk volume and data! 😱

So, if this is so risky, then why would they make it configurable in this way, you might ask?

Well, the answer is that it's to make the unit upgradable. You can start with two 1TB HDDs (which, keep in mind, the Drobo may allow you to only use just over 1TB combined total of the space of for redundancy) and then, for example, add two more 1TB HDDs later on for a total of four 1TB HDDs. You could swap one of the original 1TB HDDs out for a 2TB HDDs some time after that, and so on. The more overall space you have available across the HDDs, the bigger your actual Drobo volume can be, depending on how large you configured it to be initially. — But, this size is not directly linked to the actual size specified initially, and this is also what presents the danger with “overfilling” it, even accidentally.

This design is for expansion and versatility, though, but you do need to police it a tiny bit.

Being able to mix-and-match HDDs of varying sizes and brands in a dynamic, expandable storage array is worth it, though. Normally, a traditional RAID array might simply max out space-wise based on the initially specified configuration and couldn't be expanded without completely rebuilding it, and often times even in doing so must also use identical HDD models from the same manufacturer, meaning that you'd have to buy all new drives of a larger size for more storage.

Drobo units do fail from time-to-time

Keep in mind that Drobo units fail all of the time for people, apparently. Just search the web… you'll find tons of stories.

But, HDDs also fail all of the time on their own, and that's not Drobo's fault. So, please… always have a “backup of your backup” as I mentioned at the beginning of this post and re-referenced again so far several times. 😄

Be careful when choosing which HDDs to buy

Perhaps a shipment of HDDs was mishandled in shipping and subjected to higher than acceptable physical-shock. Perhaps a batch of HDDs from the manufacturer were faulty and they haven't discovered this yet.

These are just a couple of situations in particular that you do not want to have to worry about. Rather than setup your entire RAID array or Drobo in a weekend… order the HDDs over the course of at least a month or two, and from different retailers. Check the manufacture dates on arrival and be sure that they are all from different months. I know, I know… this may sound paranoid, but it's better to be safe versus risking a premature partial or total array failure.

Manufacturer/model recommendations

Drobo actually keeps an up-to-date list of recommended HDD models on their website, but things may move over more toward SSDs (solid-state drives) in the near future, which generally have different reliability metrics.

I personally usually opt for “enterprise-level” HDDs. These are more often slightly louder (noise-wise) when operating, but have a solid warranty and are overall pretty reliable. In general, the more expensive the HDD, probably the better. Some are way overkill for personal-use and offer higher performance than what you need (or that the Drobo can even take advantage of), though, so maybe don't overshoot it. — My personal HDD of choice right now is the Western Digital RE4 1 TB Enterprise Hard Drive: 3.5 Inch, 7200 RPM, SATA II, 64 MB Cache, as the “RE4” line is also recommended by Drobo. — These cost about ~$100 USD each at the moment.

Western Digital Re (logo)

I used to use “RE3” HDDs (the previous generation) when building RAID arrays, and have had good luck with them, so I trust the “RE4” HDDs, as well. You should still order each HDD from a different retailer at a different time, though, to be on the safe-side, as mentioned above! — If a “RE3” or “RE4” HDD fails, Western Digital has an online support portal through which you can request a replacement HDD instantly during the warranty period.

The warranty on these HDDs at this time of writing is 5 years! All HDDs will probably fail eventually, but that is a massive lifespan in which you'd receive a complimentary replacement, and you can gradually swap them out with new ones in the Drobo setup over time, anyway.


A properly configured and ventilated Drobo that is taken care of, I imagine, will be a very reliable device. I have not had any catastrophic failures so far with the Drobo S, but it is also one of their older 2nd generation products at this point. This is probably an upside, as it has had ample time for debugging, but your results may of course vary. I wouldn't be writing about the Drobo if I wasn't enjoying having it around thus far.

In terms of an expandable, redundant storage array, there is nothing else quite as friendly as Drobo… at least that I've found. I'm excited to see what other products they may release in the future, too! 👍🏻