NEVER Use A RAID As Your Backup System!


Photographers acquire A LOT of images, and that translates to terabytes of data that need to be saved and protected.

Like their shooting styles, their archive/backup schemes can be just as diverse. From RAID systems, like a Drobo, to triple redundant drives, to no backup at all.

One of the first things to remember is that an archive and a backup are NOT the same.

Backing Up Your Data

To borrow a quote from a fellow photographer’s blog, “Repeat after me three times: RAID is not backup. Period.”

For those who never heard of it, RAID stands for “Redundant Array of Independent Disks” or “Redundant Array of Inexpensive Disks.” And for those who use the phrase “RAID array,” thats redundant.

The concept of a RAID is to combine multiple, less-expensive drives into a single, higher-capacity and/or faster volume. It is designed for redundancy so that the array and its data remain usable WHEN (NOT IF) a drive fails. The terms 1-disk or 2-disk redundancy refers to the number of drives that can fail with the array remaining usable.

There are many different types of RAID configurations:

RAID 0: Its primary purpose: faster performance. RAID 0 spreads the data across multiple drives. For example, block A is on drive 1, block B is on drive 2), and this permits increased write and read speeds. This is called striping.
RAID 0 offers no protection against drive failure, since this mode does not write any duplicate or parity information.

RAID 1: This mode writes and reads the same data to pairs of drives which is called mirroring. If either drive fails, you can continue working with the other until you can replace the bad one.

RAID 5: This mode is about both speed and redundancy. RAID 5 writes and reads from multiple disks, and it distributes parity data across all the disks in the array. Parity data is a smaller amount of data derived mathematically from a larger set that can accurately describe that larger amount of data, and thus serves to restore it. Since parity information is distributed across all the drives, any drive can fail without causing the entire array to fail.

RAID 5 needs a minimum of three disks to implement. Since data is read from multiple disks, performance can improve under RAID 5. This makes RAID very good for video editing systems.


Other options include RAID 6 or RAID 10, but they aren’t often found in consumer-level RAID units. RAID levels 2, 3, and 4 are not commonly used anymore.

The problem with considering a RAID as your backup is that it doesn’t help you with file deletion, corruption by applications, operating system or viruses.

So if you accidentally delete a file, it will instantly be removed from both mirrored copies. If your disk is corrupted by a software bug or virus, the corruption will be done to both mirrored copies simultaneously.

Having all the drives in one box that is being served by one power supply and controller has its problems too. A bad enough power surge will probably fry all disks in the RAID. If your house burns down… well, you get the point.

A RAID is still a single device and because of that, also a single point of failure.

None of this means you should not use a RAID. Many photographers I know love the DROBO system. This is fine. JUST BACK IT UP! (I have never used a DROBO, but for another photographer’s opinion on DROBO see Scott Kelby’s post here:

A BACKUP needs to be a complete and recoverable copy of your data that resides on a separate hard drive possibly even a RAID. Just DO NOT USE SOFTWARE THAT MIRRORS THE PRIMARY DRIVE TO THE BACKUP or you will run into the same problems as above with at RAID 1. Proper backup software will perform a full backup and then hourly or daily backups of changed files.

My operating system and work disk (containing the current year’s photography) is backed up daily using Apple Time Machine software and a SEPARATE 3-terabyte drive. The drive is also plugged into its own surge protector. This software does not mirror the primary drives but backs up files and changed files. This gives you the opportunity to go back and recover something that may have been accidentally deleted.

The work disk contains ALL RAW files from the current year.

Images that are worked up for publication are exported from Adobe Lightroom and stored on my Photoshelter Archive. I trust Photoshelter and their geographically redundant archive to protect those images. If disaster were to strike, I could still export the images again from the backed up Lightroom archive.

My ARCHIVE of RAW images is stored on a separate drive that contains the last two year’s work. These images are also backed up on the primary backup drive.


Every year I rotate the oldest year off to a small portable drive. For these backups of the archives, I use Western Digital My Passport 2-terabyte drives. They are small and easily portable for off-site storage.

Basically everything exists in two or three places.

Whatever method you use for backing up and archiving, make sure that your data is stored redundantly and housed in more than one place. It will be the only way to guarantee its safety.

If anyone has any questions, feel free to ask!

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16 thoughts on “NEVER Use A RAID As Your Backup System!

  1. Looking at your diagram, am I correct that you have four separate drives coming off your desktop: one for the system software, one for work files, a third for images for the last two years and then a large 3TB drive holding everything? If so, mind if I ask what type of drives, sizes and enclosures you’re using for each of those. It also looks like you’ve foregone RAID. Are you using Time Machine for backups or making bootable backups with something like SuperDuper?

    • Hi PJ

      There are actually 5 drives attached to the Desktop machine, 4 of them are internal to the tower. (The system disk 500MB, work disk 2TB and 2 scratch disks 1TB each). The 3TB backup is external. All drives are Western Digital.

      I have a bootable backup of the system disk which is simply another internal drive that is not installed. I can pop it into a docking station that is generally used to diagnose disks if I need to boot from it. Of course since the system disk has nothing on it but the system and the applications, I can also do a pretty fast recover from TIME MACHINE of that drive if needed.

      Yes I use TIME MACHINE.

      The problem with the RAID 1 as your main drive is this. If you delete a file, it is deleted on the mirrored copy as well. Same issue with corruption. The drives in the enclosure mirror themselves in real time. The only thing a RAID 1 protects against is a crashed drive.

      RAID 5 would offer better protection and the RAID 5 draw is speed. But truly, unless you are doing a lot of video or sound work, I don’t see the need. AND even though you can recover from a crash, you should talk to people that have had to do so, IT CAN BE PAINFULLY SLOW to rebuild the failed drive. It is doing so by using parity data. It is not a simple copy to reload the data. Of course this drive would also have to be backed up. I am unclear as to whether you can recover a single deleted file from a RAID 5. Its main purpose is speed and ability to rebuild a lost drive.

      My laptop is backed up with TIME MACHINE to a portable drive. Here I am mainly concerned about the SYSTEM files and other things like accounting that I have on the laptop. I transfer daily work off each night, so I am not too worried about that. Usually by that time, worked up images are on the way to the client and have been sent to Photoshelter.

      Yes the small WD My Passport Drives are great for long term archive storage. I simply buy 2 at the end of every year. If you look for deals at Staples or Office Depot you can usually get one for about $120.00.

  2. Thanks for this article Pete – PERFECT timing for me and I plan to adapt this myself. I’ve had a Drobo, it was a nightmare, finally turning into a brick. As I rethink my backup system, I’ve gotten myself totally confused with RAID 0, 1, 5, etc. I embrace the concept of backup being more than drive failure replacement.

    If I use Time Machine to for my main backup, what [software] do you use for your on-site and off-site backups? I thought that TM could only backup a working computer – might you elaborate a bit if you drag and drop, or maybe use another program front the archived backups?



    • Hi Greg. I do not have an off site backup for the general system. The image files from each year are exported from Lightroom as a catalog to separate externals for off site. And of course all of the “worked up” images are stored on PhotoShelter.

  3. Pete,

    I have just spent the best part of the day looking for a longer term solution to back up my photography. I have learnt a lot about the pros and cons of RAID and proprietary systems to then find your article, the best on the net for my purpose. It also turns out that it is pretty much what I am already doing, though I am doing it manually. What software do you us for your differential backups? (possibly time machine? I am PC so if that is the case I will need to explore some more).

  4. Use a Seagate 1 TB USB drive, built in software allows you to choose the time of day and daily schedule of the backups to the drive. I will be using a 6 drive Raid 10 solution for a t620 enterprise server. I will be using the Seagate for a backup of the sql database. The seagate will be left in a fireproof safe with a hole in the back for wiring.

  5. Nice right up. Raid 5 is not for speed, its actually slow on rebuilds. Raid 0 is for speed then raid 1 then raid 10. Raid 0 if one drive fails you are dead. Raid 1 you can loose one drive and still keep working. Raid 6 and raid 10 can loose 2 drives with 6 being slower on rebuilds. Raid 10 is probably the best for speed with Raid 6 being better for getting more space per drive when you go past 4 drives. None are for backups but for preventing downtime and data loss.

    But I think your backup drive should be raid 6 or 10. ZFS files system is also nice to prevent bit rot. Lets say you need your backup and its on just a solo drive and that drive has bad sectors. That backup is no good. That same backup on a good raid with zfs is very unlikely to ever go bad. Of course if the building they are in blows up then its all gone so offsite is smart.

    • I think RAID 1 can be used for redundancy, but not backup. As the author here write, if you delete one file, you delete them both – this is true also of some backup schemes, though also.

      I think RAID 1 will beg you back up and running faster than no raid at all. But I am inclined to agree, redundancy is not quite the same as a backup. For day to day recovery from mistakes or misplaced files, a regular backup is better. But I am not so convinced that it replaces RAID 1 for a catastrophic failure. I think both backing up files and RAIDing systems is a best approach.

  6. Thanks for this article – I just read one today suggesting to use RAID – for now, due to the small volume of photos, I use a couple of external drives to save my work.

  7. I was about to impulse buy a Drobo and at the last minute I found your article! Thanks! It gave me the pause I needed to do some research first! I’m sticking to my three WD My Passport drives for now.

  8. Great article, its january 4th and Im sitting here wondering if I need to change my system… a disc has just got filled up, so I need to buy new ones…. I use large storage discs and back them up with chronosync, which is excellent. Many thanks for this piece, it helps to know that Im not the only one with this eternal headache! Mark (interior and lifestyle photography) (Fine leather camera straps, made in England)

  9. The biggest issue with RAID are the unrecoverable read errors.
    If you loose the drive, the RAID has to read 100% of the remaining drives even if there is no data on portions of the drive. If you get an error on rebuild, the entire array will die.

    A UER on SATA of 1 in 10^14 bits read means a read failure every 12.5 terabytes. A 500
    GB drive has 0.04E14 bits, so in the worst case rebuilding that drive in a five-drive
    RAID-5 group means transferring 0.20E14 bits. This means there is a 20% probability
    of an unrecoverable error during the rebuild. Enterprise class disks are less prone to this problem:

  10. Questions:
    Q1 a&b: What is is the problem with Raid-1 using Time Machine? …Won’t I end up with TWO Identical Time Machine on the Raid-1 external drive dedicated to back-ups using Time Machine program? … that isnt that superior to having just a single external drive back-up?

    Maybe there’s something I don’t understand in your article “NEVER use Raid for a back-up”. I will appreciate your answer as I plan to purchase a Western Digital “My Book Thunderbolt Duo 4TB Dual-Drive with RAID” to replace an older 2TB “Iomega Companion for Mac’ that I’ve using… and use the new WD MyBook external drive in Raid-1 conficuration so I always have two back-up time-machine copies of everything.

    My thought is that for additional back-up security, I could even switch out one of the removable/replaceable drives in WD “MyBook Thunderbolt Duo 4TB Dual-Drive with RAID” the on a weekly so I have also have an offsite copy thats no more than a week-old at any given time in case of fire other catrastophe at the physical site of my digital workstation.

    Any answer or further explanation will be appreciated. Thanks

    Becase the WD …. and a third off site if I follow-thru w/ the

    • RAID software instantly mirrors one drive to the other in the RAID. If your time machine backup software fails or corrupts during the backup, both sets of data will be corrupted.

      RAID gives redundancy, IT IS NOT a backup. Yes you can use a RAID array as your backup drive, BUT if the array fails you still need a backup that is stored on an entirely different physical disk. The second drive in a RAID 1 array IS NOT that different disk.

      When you configure the RAID 1, you will never see two drives mounted on the desktop. If one of the drives in the RAID fail, you will be notified by software that the drive needs to be replaced and once you do, the firmware will rebuild the mirror. RAID 1 is NOT an automatic backup!! But in situations where you cannot tolerate downtime, this will keep you running until you can make repairs.

      The best best option is to use TWO SEPARATE DRIVES for backup and let Time Machine do the work and eliminate the complexity of the RAID.

      Time Machine can be configured to work with multiple drives and alternate backups between them. This way if one of the backups were to fail, the other will be available.

      Hope this helps.

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