If you’re in the video world you might have heard about a NAS (Network Attached Storage) and a SAN (Storage Area Network). This article tries to help you answer the question: SAN or NAS? Which one’s right for you?
Part One covers the definitions and basic differences.
First, a disclaimer: I’m not an expert in either a SAN or a NAS. My understanding is, to put it simply, my understanding. This could be wrong or inaccurate. Like you, my first priority is video, and I don’t have the time or brain power to figure out the complications of a SAN or NAS before I invest in them. I want the bottom line, and this is my attempt to understand which is which, and which one I should be interested in.
The problem of understanding a SAN or NAS is like a tree. You can’t get the whole tree without doing a bit of digging. Let’s try to dig without getting dirty.
The birds and the bees
Contrary to popular belief, the choice between a NAS or SAN is not similar to a Pepsi vs Coke battle, but more like a Pepsi vs Mirinda battle, where Pepsi is orange in color.
I’m sure this analogy doesn’t make much sense. That’s the point! Don’t get mad at me, let me redeem myself by explaining.
Let me use a better analogy to help you understand. Since we’re in the subject of nature, let’s choose the birds and the bees as our Muses.
In the beginning, there was a bird and a bee:
Birds of a feather flock together, so they look like this:
Nothing fancy, just regular chums hanging out.
Birds and bees don’t communicate globally by email or Facebook. They tend to remain as local groups. Let’s call this group a Local Area Network, or LAN. Here’s one version:
Straightforward enough, right? Birds have pals, bees have pals. They stay connected in various permutations and combinations. No big deal.
They have to eat, so they gather food. They also need to store food somewhere. This is how they do it:
How do bees and birds use their storage areas? Here’s how:
Wait a second, that’s a big difference, isn’t it? Of course it is. Bees have one home, where they make excess honey anticipating the future winter. Birds prepare nests to feed their young, but otherwise just hang around on trees in groups. Now, here’s the killer:
Unlike a beehive, where each bee works for itself and the other, birds tend to be selfish creatures. They don’t interfere in each other’s storage areas. I mean, they could, but it’s frowned upon. A bird that acts un-bird-like is an outcast.
Now, let’s assume both groups (LANs) want to grow their storage areas. This is what it’ll look like:
Interesting. Who is the captain of both these storage areas?
In the case of the birds, each couple is in charge of their own nest. In the case of the bees, the Queen bee is in charge. Let’s leave our birds and bees, and replace them with computers:
Don’t be shocked. Look at the colors:
- Bees and Birds act like computers connected to a LAN.
- Blue stands for one NAS. Six blue boxes = Six NAS systems.
- Orange is the whole group of bees, or the hive. One big orange box = One SAN system.
- Pink is the captain. In the case of a SAN (bees), there is only one captain. Each NAS system has its own captain.
- The pink arrow lines are ‘demands from computers’ in the network. In a SAN, they have to go through the captain. It’s the same for a NAS!
In a SAN your storage systems can be of different types: drives, tapes, whatever. They are all pooled together and managed by the captain. A SAN acts like one big hard drive.
A NAS can also have different types of storage: drives, tapes, whatever. But each NAS is designed to only hold one type of storage, and they behave selfishly.
SAN or NAS? What’s the difference?
Ready for the fundamental definition? The answers are in the names themselves! Look:
- SAN – is a Storage Area Network – is a Blah Blah Network – is a Network
- NAS – is a Network Attached Storage – is a Blah Blah Storage – is a Storage
A SAN is a network of storages (network of drives or drive systems or tape systems or whatever), while a NAS is storage (either drives, tapes, whatever, but only one kind) that is part of a network. It is from this fundamental difference that their major properties arise:
- Each computer connected to a LAN feels like the SAN is its own (bees feel the whole beehive is their own).
- Each NAS connected to a LAN is separate, and don’t care about each other. A computer that connects to the LAN will have to ‘reach out’ separately to each NAS. This makes the computer feel that the NAS is a shared thing, and not its own.
- If the captain of the SAN goes down, the entire SAN fails.
- If one NAS fails, the other NAS-holes don’t care.
- You can detach a NAS from the LAN and nothing much happens.
- You remove a whole SAN and the computers no longer have access to your centralized storage.
- When a SAN grows, it physically consumes more space.
- Both SAN and NAS systems are designed for LANs only (studios, post facilities, etc.), and not for Wide Area Networks (College campus, the Internet, etc.).
The way a NAS or SAN ‘communicates’ is different. Bees and birds speak different languages. They can’t talk to each other. Here are some properties:
- Since a NAS is expected to be plugged-in to a LAN wherever the need arises (different rooms, or even across the globe to another LAN), it follows standard protocols (like HTTP, TCP/IP, NFS, etc.) that works over regular Ethernet.
- Since a SAN is expected to stay put in a facility, and many computers access them at once, speed is of the essence. For this reason, you’ll find many SANs using Fiber Channel over protocols like SCSI, etc.
You see now? They are designed for different usage scenarios, and the underlying technologies try to match those requirements. When seen from afar, they all look the same, which is what I meant by the Orange Pepsi vs Mirinda analogy. If you can’t be bothered to dig deeper for the whole tree, then you don’t get the tree.
In Part Two we’ll look at how the fundamental differences between a SAN and NAS affect how we choose them for our video work.