Story and Photo by Jeffrey Smith
For the past 15 years, I have used a Drobo 5N NAS device to store my photographic files and files for the magazine I edit, the NRHS Bulletin. In early 2023, Drobo closed shop, so I began evaluating new equipment. I found a dizzying array of options and technical terminology that must be difficult to navigate for those who are not technical. I hope this column and one that follows in the next issue explain the basic technologies and provide some simple guidance on which direction is best for your situation.
I won’t get into specific product recommendations, as there are plenty of sources for that information on the internet. We are going to focus on explaining the underlying technologies that the various products utilize and then offer some guidance for what might be best in different situations. I am also summarizing, so don’t get too tied up in the specifications; there are exceptions to the speeds and certainly pricing that I quote in this column.
There are three general strategies for storing your images. The first is to use a network-attached storage (NAS) device that is accessed through a local network (LAN) in your home. The second is to utilize external hard drives connected directly to your computer. The last is cloud storage where your images are on someone else’s server and where you pay a recurring fee for keeping the images there; the cloud provider takes on the task of ensuring redundancy, and recovery strategies are in place based on the service level they have sold you. In the first two strategies, these tasks fall to you.
NAS Devices
An NAS device is a stationary device that contains multiple hard drives within a single enclosure. Typically they hold between two and eight drives but some hold more. They have their own operating system, processor, RAM, and one or more ethernet connections. These ethernet connections can be bonded together to function as one network connection operating at a higher speed than a single connection. If you need storage beyond the capacity of the NAS you select, many offer expansion capabilities where you can add an enclosure that increases the number of physical drives that can be attached. NAS devices vary widely in price from $250 for one that holds two drives up to thousands of dollars for devices that hold eight or more drives. For most photographers, a two- or four-bay device (each bay holds one hard drive) is adequate and can be obtained for $200 to $500 (not including the hard drives). Most NAS devices can utilize traditional mechanical hard drives (HDD) or solid-state drives (SSD).
One of the main reasons NAS devices are preferable is the fact that they can be configured to use Redundant Array Independent Disks (RAID) technology. RAID was once very expensive and technically complex to set up, but NAS devices and software have made it easy to use for nearly everyone. RAID is based on a mixture of three basic concepts. First is striping or splitting data evenly across two or more disks. The second is mirroring, the replication of logical volumes across separate physical disks in real time to ensure continuous availability. The last is parity, which is used to achieve data redundancy for recovering from a drive failure. If a disk fails, the data on the other drives can be combined with parity data to recreate the missing data. This can allow one or more drives to fail without encountering data loss.
When you set up a NAS device you will need to decide what RAID level to utilize. This will also impact the number of hard drives that you need to purchase and also how large of a NAS device you will want to purchase. For instance, if you want to use RAID 5, you will need at least three drives and thus a two-bay NAS enclosure will not work. So, what RAID level should I choose? Here is a guide to each.
RAID 0 – This stripes data across two or more disks without parity, and thus does not allow for any redundancy. The failure of one drive causes the entire array to fail. This is used where read and write speed are most important and data loss is not a concern. I would not recommend this approach for storing photography files.
RAID 1 – Mirrors data across two or more disks. The array will continue to operate as long as one disk is operational. It is typically used where read performance is more important than write performance and basic protection against data loss is desired. This is the minimum level of RAID that I would recommend a photographer utilize. This can be implemented with a two-bay NAS device.
RAID 2, 3, and 4 – These configurations are rarely used commercially so we will skip the details.
RAID 5 – This level uses block-level striping with distributed parity. Here, parity information is distributed among the drives and requires all drives to be operational except one. If a single drive fails, future reads can be calculated from the distributed parity such that no data is lost. RAID 5 requires at least three drives and thus a four-bay NAS device (three-bay NAS devices are not very common). This is a very popular option because it provides a good level of redundancy and recovery without significantly degrading speed. It is the option I would recommend for most photographers if you use a NAS.
RAID 6 – This level uses block-level striping with double parity blocks distributed across all disks in the array. Read speeds are good with this level; however, write speed takes a penalty due to the more complex parity calculation. This level requires a minimum of four drives, and thus at least a four-bay NAS device will be needed. Due to the double parity blocks, two drives can fail and the array will continue to operate
Backup versus Redundancy
It is important to understand that RAID is not a backup strategy. RAID is a way of using redundant data and automated recovery processes in the event of a hard drive hardware failure. Your backup needs to be in a separate physical location from your NAS. Additionally, it is not necessary for your primary and backup to utilize the same approach. Your primary could be a NAS and the backup an external drive.
External Drives
External hard drives are devices that contain a single drive inside of an enclosure that interfaces with your computer via a cable (USB or Thunderbolt in most cases). Some require external power while others do not. They generally come in two types. One has a traditional hard drive (HDD) in it while others are based on solid state technology (SSD) where there are no moving parts. While storage capacity is the biggest variable with external hard drives, there are a variety of other factors that impact cost, speed, and reliability which we will cover shortly.
A small number of external hard drive manufacturers (SanDisk Professional is one example) offer external drives that have RAID capabilities but are portable units that connect to your computer via USB or Thunderbolt. These drives can provide the redundancy and recovery benefits of a NAS with the portability of an external drive. The trade-off is cost. These external drives are on the expensive side, and in many cases, exceed the cost of entry into a NAS which has significantly more features and options. But, they could be a good option for users willing to pay a premium for portability.
Hard Drives
Hard drives are not all the same. Their reliability varies as widely as their price, and there are a few things to consider. Let’s talk about HDDs first. These drives store data magnetically on a platter and use an armature to read/write data as the platter spins around. HDDs have an RPM speed, typically 5,400 or 7,200, which determines how fast the drive can access and transfer data; 7,200 RPM drives are the fastest but cost a little more and can wear faster. Additionally, drives are engineered for how they will be used. Some drives are intended for continuous operation, and these are most appropriate for use in a NAS. Examples of NAS drives are the Western Digital Red brand and the Seagate IronWolf brand.
SSDs are based on a newer technology that does not use platters and has no moving parts. It stores data on flash memory, very similar to a memory card used in a digital camera. There are various drive speeds measured in Gb/s. For instance, a SATA III drive will transfer data at about 6GB/s. Like HDDs, the faster the drive the higher the price. The advantage is that they are more durable, faster, smaller, and use significantly less energy than HDDs. The tradeoff is that SSDs are always significantly more expensive than their mechanical counterparts, currently about double the cost.
Now let’s look at external hard drives. Their speed is largely determined by the connection protocol it supports (USB 2, USB 3, Thunderbolt 3, and the like). Additionally, you have to look at what your computer supports. If your computer is USB 2, then a USB 3 drive will only operate at the USB 2 speed. To generalize, the actual speed you will get is the slower of the speed of your hard drive and the computer.
There are consumer-grade drives such as the Western Digital Elements Desktop drives. While these are generally reliable, there are also Enterprise drives that are engineered for a higher level of reliability such as Western Digital’s SanDisk Professional drives. At the time of this writing, a SanDisk Professional Enterprise drive is about $100 more than the consumer version for eight terabytes of storage. The added reliability and durability are probably worth the money.
Coming Up
Next time, we’ll discuss cloud storage and the advantages and disadvantages of the different types of storage