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The Wonderful World of Local Backups (Part 2 of 2)

Matthew Morse's picture
August 10, 2015 - 9:00pm

In my last post, I began a review of several of the local backup options that I have employed over recent recent years, starting with a simple external hard drive and moving onto Drobos. In this post, I’ll review two additional options I’ve explored and setup: Time Capsule and a Network-attached Storage (NAS) device (in this case, setup as a RAID array).

In this segment, we’ll shed some light on a couple of additional options for those seeking local backup solutions

It bears repeating that, whatever my local backup option, I always use an additional online backup option such as Backblaze to provide an additional offsite duplicate.

Time Capsule and Networked Drives

For anyone who appreciates the simplicity of Time Machine, but dislikes the burden of constantly plugging and unplugging an external drive, then a Time Capsule or networked drive may be a great option for you.

If you aren’t familiar with Time Capsule, this is an out-of-the-box solution made by Apple that combines a wireless access point with a built-in hard drive. This option is perfect for someone building their home office from scratch, as it gives you two devices (a wifi router and an external hard drive) together. For those more familiar with Apple’s product labels, the Time Capsule is basically an Airport Extreme base station with a built in hard drive.

The downside, of course, of having a two-in-one device is that if one breaks, you’re stuck repairing or replacing both. Although I have had access points die on me, it’s far more likely the hard drive will fail long before anything else has a problem, in which case any local computer shop would be able to replace the drive for you (or you could do it yourself, if you’re handy with electronics).

If you like the concept, but want to keep the components separate, then you can use a wireless access point (such as an Airport Extreme) that supports wired network drives. Simply plug an external hard drive into the device’s USB port, configure it as a network drive, then you can set it up to serve as a Time Machine drive that performs just like the Time Capsule.

These options are great for laptop users, as your device will automatically backup whenever it’s on the network, without having to remember or worry about plugging in drives. The major downside is that you are still dependent on one hard drive with a single point of failure — if your hard drive croaks, then your backup is toast. This is why I went for a NAS RAID array.

Network-attached Storage RAID array

Network-attached storage (NAS) devices are sold in a number of flavors and sizes, but for the purposes of this review, I’m referring to those that include two or more hard drive bays, for reasons that will become apparent.

NAS devices are like the swiss army knives of data storage — you have a large number of options for what kinds of functionality is provided. Similarly, they’re the most complex to setup, but that doesn’t mean they can’t be easy, fun, and useful!

The particular device I’m using is a QNAP, such as this model found here [affiliate link]. Most devices of this nature offer the ability to setup a RAID 5 array. Put in plain English, a RAID 5 array is simply a redundant file structure using multiple drives. So, if a single drive fails, the other drives contain backups of your data so you don’t lose anything while you replace the failed drive. If you really want to dive in, there are also different types of RAID levels you can read all about here, which mostly relates to how many drives are used and how many failures are supported, but that's mostly for the power users.

If this sounds similar to Drobo from my last review, it’s the same concept, but with one important difference: unlike Drobo, RAID 5 arrays are not proprietary. If your device croaks or you want to change manufacturers, you can remove those drives and they'll function in another device from a different brand. You’re not locked into one company when it comes to data protection.

The downsides of a networked RAID 5 array are otherwise similar to a Drobo, namely: cost (not only of the device, but the drives you put into it), and the fact that you’ll lose a fraction of disk space in order to support that redundancy. Many RAID 5 arrays also require use of drives of the same size and have more limitations on their expandability than Drobo.

[Editor's Note: With a RAID 5, generally all drives must be the same size, but with some systems if you have varying size drives, then the smallest drive becomes the template for the rest — clearly not an ideal way to go (i.e. if you have three 5 TB drives and one 3 TB, all drives will be treated as 3 TB). In a RAID 5 set, one drive is called the parity drive and is “lost” from storage, so if for example you only have only two 3TB drives as RAID 5, then you'll only have 3 TB of storage. But if you have three drives, you'll have (3–1) × 3 TB = 6 TB; if you have 10 drives you'll have (10–1) × 3 TB = 27 TB, and so-on. Drobo on the other hand lets you mix and match drive sizes, however as I noted in the Editor's Note in part 1 of this article, I heavily, heavily discourage users from buying Drobo. I and many other photographers have lost precious files to these proprietary systems. –Joseph]

There are additional advantages to a networked device, however. These devices are plugged directly into your home’s network, which allows you to backup wirelessly to Time Machine. QNAP (and other manufacturers) also include pre-installed tools for managing a Time Machine segment, which allows you to set and modify the size of your storage space dedicated to a Time Machine backup. The device also includes a slew of features beyond backup, including the ability to store music and videos & stream that content from the device over your network or through an HDMI cable directly to your TV.

This doesn’t begin to touch on the capabilities of such a device. If you’re a geek, you can configure any number of different functional options — the sky is the limit. My point, however, is that you don’t have to be a geek to enjoy the benefits of this device. If you just want a simple place to backup your stuff with redundancy and maybe stream some music and videos, you can do so very easily out of the box without an unreasonably high level of technical skill. It took me about 15 minutes to get up and running.

Granted, this is still an expensive option and one likely reserved for the power users and truly backup-obsessed among us, but if that applies to you, then give it some consideration. I’m only sorry I didn’t do it sooner.

About the author, Matthew Morse:

Based in Washington, DC, I'm the operator of the travel photography blog The Prodigal Dog. I'm a digital strategist who has been an avid photo hobbyist for over 15 years. Hiking and traveling off the beaten path, landscapes, wildlife, and the occasional portrait are my preferred subjects. Always interested in the technology behind what makes this art form so great.

Backblaze Time Machine
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Matthew Morse

Matthew, Nice review.  And Joseph, thanks for the editor comments.  Very informative.


Florian Cortese

I used a Synology NAS as a Time Machine backup for awhile. The backups seemed to work fine but I like to peer into the backups from time to time to see what’s going on. Time Machine backups on a NAS (at least on the Synology) are stored as a sparse disk image. That means you need to mount the image to view the files in the Finder. I could never get it to work reliably. Sometimes it would take forever to mount and most of the time it would never mount. It didn’t leave me with a warm and fuzzy feeling about my backups.

Somehow Time Machine was able to mount the sparse disk image to do the backups. Eventually my 16TB RAID ran out of space to do further backups. Why? Because Synology recommends creating a time machine user with a space limit so it doesn’t completely take over your NAS. The Synology could only create a maximum limit of 4TB. My files to be backed up were not even half the 4TB size. However over time it bloated to the 4TB limit because of older versions and for some reason Time Machine wasn’t able to delete old backups to make space for new.

In the end I just gave up on it. I bought a 5TB USB drive to use for Time Machine. It provides the regular hourly backups without any thinking. 

I still use my NAS for yet another backup. But I use Chronosync to do the backups. I can look into the backups anytime using the Finder since it doesn’t create a sparse disk image.

Oh, and I also use Backblaze.


Thanks for your comments! I'll have to look into the disk image issue for NAS-based Time Machine backups, as well as the space limitation options. Haven't run into any issues yet, but these are great points and better to know now than stumble across them later.

Thanks for the review. I actually researched tonight how to back up my Time Capsule. I knew this was necessary because I lost my Airport Extreme Base Station hard drive around 10 month ago and could not rebuild it. So, I discovered that in OS X you can select two disks to have Time Machine back. Both are networked. My 3 TB Time Capsule and my Drobo 5N (Yes Joseph I agree about the proprietary issue, but I also prefer ease of use and options with the Drobo). I originally had this set up with 3- 3TB Red Drives, but added 2- 6TB Red Drives and set the Drobo up for Redundancy. According to Drobo, a three drive failure would still be protected.  Next step is selecting an on line backup like Backblaze or CrashPlan. Your topic and comments came at a great time. Thanks.  Jon

I was used to the ease of Aperture and the concept of Vaults. This worked flawlessly. However when moving to Capture One I had to invent a new backup solution which works without much hassle. What I have now is the following.

I have 2 NAS devices. On one I have my working copy of my photos. I attached this to my iMac by ISCSI. A volume from the other NAS for backup I have also connected by ISCSI. With ISCSI the volumes appear as local disks. I have Carbon Copy Cloner to copy the contents from the first volume to the second volume on a schedule. This can also be triggered manually. And for the second copy (one copy is never enough!) I have a USB3 drive. With a special feature in CCC my photo library is copied automatically when I attach the drive. This way I don’t have to do much myself to make backups.

I read in the article about RAID. Because I have a storage background I would like to say a few things. First of all, a RAID array is not a backup. Disk is an active medium. If your controller decides to write junk nothing is there to stop it. The best backups you can make is on a specific backup medium like tape. But since tape and tapedrives can be expensive and a hassle to work with people tend to make backups on disk. I do too.

This makes a good argument to make more than one backup. Preferably one on another location. When your house burns down with all copies inside, you sill lose your data. I don’t say that I think it will happen but you will pull out your hair when it does. My second backup is not outside my house but I don’t need to carry my NAS outside. I have an external disk.

A good practice is to have multiple manufacturers. When buying a bunch of (the same) disks at the same time you will probably end up with disks from the same lot which can fail around the same time. When multiple disks fail in an array, again you will lose your data. This means that you are better off with different manufacturers and/or solutions. I have Seagate disks in the first NAS, WD NAS disks in the second and a Verbatim external disk.

One more note: RAID5 is best for smaller disks in my opinion. Why? Because the rebuild times. When a disk fails and you put in a new disk it will take a very long time before the array is healed again. This can take up to multiple hours. I have seen rebuild times with 3TB disks of 24-36 hours. During that time (and the time getting a new disk) you are at risk. When loosing another drive in the mean time your data is lost. With larger disks it is better to use RAID6. With RAID 6 two disks may fail and you still have your data. But this means sacrificing capacity for redundancy. When you have 6 3TB disks, you end up with 4x3=12TB of storage. Still RAID6 with even larger disks is also not a good solution, again because of rebuild times…

Just my 2 cents in a storage discussion. I’m not saying everybody is doing it wrong. I try to supply information people may not beware of of have thought about.

I am using two 8TB NAS (raid 5)  units for backup, and have been for several years.  I initially used “Time Machine” to backup up.  But decided to test how the sparse bundle that is used by TM would “rebuild” if there was a disk failure (using raid 5).  So I pulled a disk and installed one of the spare drives I keep on hand.  Simulating a disk failure, and replacement. The sparse bundle did rebuild, but it did not contain any data, all the TM data was lost.  Not good for a backup.  My conclusion was that the TM should only be used on a stand alone disk, since the data will not be rebuilt on a raid disk failure.  If any one of the 4 disks in the raid fails  all backup data is lost.  If I were going to use the TM I would use 4 stand alone drives, and select them all as backup up drives. That way I would have to loose all 4 drives before loosing my backups. As it is I use ChronoSync and am pleased with its performance over a network.

The same hold true for an ISCSI volume created on a NAS until.  The data will not be rebuilt (raid 5) if a HD fails and is replaced.  I tested that also.


Interesting test. I have a Drobo 5N, and set this up as a second Time Machine backup for two computers. Drobo specifically encourages this and includes this option as part of their ‘software’. I wonder if they have solved the problem that you discovered with your NAS units. I’ll copy them with your comment and find out.



I’m a believer in testing backup systems.  If it hasn’t been tested then you aren’t backed up. So what I would do is make sure I had a duplicate copy of all my data, then simulate a HD failure.  See what happens.  I can tell you horror stories about people that were smug with the thought that everything was backed up then when the time came found out the backup system was flawed.  A couple of those stories are mine.

I agree. I just submitted this thread to Drobo tech support and will let you know their reply. I’ll test it but I want to hear from them as well.  What’s the point in promoting something that is doomed to fail? Of course I’ll test this as well. 1st step..

So I just heard bac from Drobo. ‘Should work…’ Not the same as does work.  

Hello Jon,

Thank you for updating. It should operate normally as it should.

Kind Regards,
Stephen P.
Technical Support Agent

Drobo Documentation: ;
Drobo Resources:
Transporter User Guide:

Customer Jon Kirshner via CSS Web  09/09/2015 03:11 PM 

Stephen, thank you for your feedback. I do have my 5N set up for dual disk redundancy. The specific question is whether or not the Time Machine Sparce Bundle backup on the 5N will properly operate as though it was on Apple’s Time Capsule or a single disk? Have you ever tested to see if you can completely ‘reset’ a Mac using Drobo’s 5N Sparce Bundle ‘back up”?

Response Stephen via Email  09/09/2015 12:41 PM 

Hello Jon,

Thank you for contacting Drobo Technical Support. The Drobo is designed to be able to protect your data from a drive failure at any time, this also includes your Time Machine backup data as well.

The Drobo does not save the data to only one location but to all drives in order to make sure that data is not lost should a drive fail, when you have created a backup volume on the Drobo this applies there as well.

For even more protection you could set the Drobo into Dual Disk Redundancy changing the Drobo to a RAID 6 making it so you can lose 2 drives at a single time without data loss.

If an issue like this has occurred it would be best to create a case on it for us to look into as there have been no reported issues that a single drive failure caused the Time Machine Volume to be lost.

- See more at:”


I would be interested in hearing how your test turns out.  My two NAS units are using a Linux file format.  Ready NAS Ultra 4+, and a Ready NAS Pro 4.  They have about ~ 37,000 Hrs on them and have been working flawlessly still with original disks.  They are only used for backup, and I’m sure when one disk fails the others will soon follow. Like your device theses “support” the TM, by that I mean there is a checkbox to create a sparse bundle that will “grow” to a set size that is user selected.  These were purchased 01/2011, I’m not sure when I actually tested the the TM backup.  Since there has been several updates to the OS I may be tempted to give it another test.  


I ran another test on the TM sparse bundle, and am pleased to say that it restored the data OK.  I first backed up approx.  350 GB, then removed a disk from the array and installed a spare.  After resync all the data was there.  I deleted that TM backup then backed up 1.7 TB for a week,  pulled the spare and re-installed the original disk .  After resync was completed, all the data was present.  Much different than the last time I did the test several years ago.

Mike, great work. Now we can all sleep.

Thanks for your diligence.



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