In Part One we learnt the difference between a NAS and a SAN. This this part we’ll use that understanding to find out which of these two solutions fits typical video workflow scenarios.
How SAN or NAS handles data transfer
Let me bring you back to the orange Pepsi vs Mirinda analogy. If both of them look alike from afar, how do we tell them apart? One simple way is to look at how they handle files.
Let’s imagine you want to go backstage to get an autograph from your hero. There are two ways it can be done:
- You are given a backstage pass, you meet your favorite star and get the autograph from those divine hands, or
- You are asked to wait outside while your cap or handkerchief or whatever is taken backstage, and then brought back with a signature.
In the real world, if the autograph represents data, there are two ways it can be had:
- Through a server (like getting a file off the internet), or
- Getting it directly from your hard drive.
In the first instance you need a browser (HTTP) or FTP to reach and download the file. In the second instance the file is directly available to you. So –
- SAN – acts like your personal hard drive.
- NAS – acts like a server, which it is.
As we saw in Part One, a SAN is built for speed and reliability. To make the SAN behave like your hard drive, you’ll have to eliminate the middle man – the Operating System/File System. A SAN actually lets you reach and take what you want from a hard drive directly. The technical word for this is: having block-level access – the ability to read files directly in blocks (many at a time) to get the fastest data transfer possible.
Note: The file system isn’t eliminated, of course. You always need a file system.
A NAS, on the other hand, is a server, which must have an Operating System and a file system. To get something from a NAS, you must go through its rules, which is called a protocol.
What you must ask then, are the following critical questions:
- What connection is used: Fiber Channel, Ethernet, etc.
- How would you get that on your computer?
- How much data do you handle?
- How many people work with the same data?
- How many computers will be used simultaneously?
- Do all the computers have the same connections as your SAN or NAS?
- Do you use Macs, PCs or both?
- How much money and time do you have?
- How much space do you have?
- If it fails, how much downtime can you suffer?
- What’s your backup strategy?
The answers to these questions within the context of what we’re going to look at next will point you in the right direction.
When to use a NAS or SAN for video work?
For the sake of simplicity, we can divide workflows for editing and finishing into the following groups:
- On-set data station
- Single computer or laptop
- Small production company (2-5 computers)
- Post house or studio (5+ computers)
- Large VFX facility (50+ computers)
Let’s look at them one by one:
On-set Data Station
This is a device or computer that needs to ingest, transcode and backup data. The traffic is usually from the computer to the drives. Traditionally, the fastest way to do this by using a DAS. Connect all your disk arrays to your computer, and that should be enough. When data does need to travel to a video village or monitor or switcher, the established system is HD-SDI.
There is no network involved, so both a SAN or NAS is unnecessary.
The same logic holds as above. There is no network involved, so it is pointless to use a NAS or SAN where a DAS will serve you perfectly.
If you compare this to a NAS, the Gigabit Ethernet connection will prove to be far slower than a USB 3.0 or Thunderbolt port. Here is how they compare:
|Speed of one 7,200 rpm drive||120|
*Except for the hard drive, all speeds are maximum speeds. Read-world performance is always lower.
A 1 GbE connection (what you get on most computers) is only as fast as one hard drive (actually much lower!). At some point you must ask yourself: Why would I connect four drives in RAID and then bottleneck myself with a 1 Gbps connection (a NAS), when I have USB 3.0 and Thunderbolt at my disposal?
Production Company (2-5 computers)
Let’s say you have three computers for editing, one for finishing and the third one as your ‘office’ computer or whatever. For some reason you want all of these to have access to a shared storage.
You’ll need a SAN if you:
- Can afford it.
- Need all editors and computers to access the same data. It is very rare for a small production company to have their editors working on the same project!
- Anticipate scaling your storage in the future.
- Work with footage that has a data rate greater than 150 MB/s, all the time.
Take a look at our chart above. Is a super-expensive SAN really worth the price; say, over a few Thunderbolt or USB 3.0 DAS systems? What happens if you spend your last dollar on a SAN and it goes down?
You could play Counterstrike while someone fixes your SAN…oh but wait! Your saved games were in the SAN!
What about a NAS? You’ll need a NAS if you:
- Need only some of your computers to share the same data.
- Need to move that box around for some reason.
- Can live with 1 GbE speeds and weird file systems.
- Can afford a 10 GbE NAS if you need Thunderbolt-like speed.
At what point does a NAS make more sense than, say, a DAS or an Apple 3 TB Time Capsule?
These are questions only you can answer, based upon your clientele, workflow, business model and ambitions. My advice? A small production company with 5 computers don’t need a NAS or SAN for daily work. If you want a centralized backup system, that’s another thing. You can always build a cheap backup and archival system.
Post house or Studio (5+ computers)
If you are post house with more than five computers, the chances are you have multiple computers dedicated to one project. At any given point you might be moving between editing, color grading, effects, audio, a few render nodes, and so on.
It is for this scenario that SANs make sense. Even it ‘makes sense’ for smaller post facilities, it wouldn’t make sense once you look at the price tag. But, if you’re a successful post house that works with so much data that moving hard drives around is no longer fun, it’s time to get a SAN.
A SAN will:
- Help you scale.
- Get you critical support and updates as and when required.
- Give you speed per node, with a reliable infrastructure to back that 24/7.
- Keep things compact and neat.
- Help you work without needing servers. You can use your computers to directly interface with the SAN.
- Churn out work as fast as you can using a DAS on one computer.
- Take away the pain of troubleshooting.
What a SAN really does is it allows you to continue working as if nothing has changed, even when you add multiple computers and people. A reliable solution takes the complexity off your shoulders. It’s only in this scenario that the price of a SAN pays off.
The decision is easy. If you can’t afford a SAN, then you can’t afford it.
Unless you have a brilliant IT wizard who can put together a SAN, ensure it interfaces with your computers, operating systems and workflow, and is able to discover problems and correct them in less than 24 hours, don’t try to build a cheap SAN.
What about a NAS? Would that do any good? A NAS will:
- Help you divide your studio or post house into pockets.
- Get you some kind of support.
- Keep things somewhat compact and neat.
- Slow you down unless you have methodically planned its use.
- Not help you scale.
- Not keep things compact and straightforward.
- Not feel like a DAS.
Breaking down your workflow into NAS units is, in my opinion, not very different from having DAS units. I don’t recommend it for this scenario. A NAS is beneficial for backups and archival, but I don’t see the benefit of a NAS for a small post house or studio.
Large VFX facilities (50+ computers)
Large VFX facilities have custom-made network infrastructures that simply must have a SAN. The best way to visualize data flow in such a facility is by looking at the electrical wiring. Electricity flows through every cable to every station, light and air-conditioner – that’s exactly how data must flow for any work to get done. It must appear and be seamless.
So, what’s the bottom line? As far as I understand, I prefer a DAS for all small work groups – it is manageable, even when working with 150 MB/s footage. An 8-bay Areca ARC-8050 Thunderbolt NAS/DAS hybrid costs only about $1,700, and you can stuff 32TB of data in there. If you’re on RAID 6, you get about 24TB, and that’s 44 hours worth of 150 MB/s footage.
With the price of DAS systems falling rapidly, it is almost criminal to complicate your life unnecessarily by investing time, money and effort into either a NAS or SAN if you absolutely don’t need it 100%.
When you grow into a larger post facility, with many people accessing the same data, a SAN is definitely the right way to go. You could also justify a SAN as a backup system rather than as a ‘work’ system, but that’s a call only you can take (It’s expensive!).
As for NAS units, I’m beginning to believe they are unnecessarily complicated for video work. They’re not cheaper than a DAS, nor much cheaper than a SAN all things considered. I’d stay away from the 1 GbE Ethernet NAS units that are primarily intended for business storage and archival. Video demands better speed and throughput. A DAS gives you that easily. When it’s time to move to a SAN, you’ll know.
What do you think? Is there any scenario I’ve missed where only a NAS will fit?