NOTE: Over the past few years, I have received a lot of messages and comments about this post. It is possible I did not make clear what I was trying to convey about RAID.
ANOTHER NOTE: I have redesigned the site and for some reason, the comments are not showing. I am working to get them restored.
What I am trying to say is that many people use a RAID as their primary storage system, and have it configured either as a RAID 1 or 5, thinking that the redundancy of the RAID is a backup. THIS IS NOT A BACKUP SYSTEM. This was the point I was trying to make.
So in that vein, I am retitling the post. A RAID IS NOT A BACKUP. Yes it can be used as a backup destination, but the redundancy is not a backup in itself.
UPDATE: As for my current 2018 setup, I am running an iMAC with a Retina 5K Display and a 3.5GHz Processor with 1TB Storage. The daily work for the year is stored on an external 5TB drive. That drive is backed up daily using Time Machine. Every month or so (depending on workload) the backup is backed up to a WD My passport Drive and that copy is moved offsite to a safe deposit box.
Past years are stored on two WD My passport Drives. One in a waterproof Pelican case at home and the other in the safe deposit box.
All worked up images are also stored on PhotoShelter.
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: scottkelby.com/2012/im-done-with-drobo
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!