Network Attached Storage (NAS) – The Untold Truths
With the constant requirement for increased disk capacity we are seeing an upturn in the usage of external storage devices. Many customers are purchasing USB drives or Network Attached Storage (NAS) devices to provide a solution to this problem. USB drives are hard drives that installed in a case and commonly known as “external drives” and connect to your computer by a cable via your USB port.
While this post is not really covering USB drives, our recommendation would be to ensure they are USB 3 or better. Basically the higher the USB version, the faster you can transfer data. Remember you’ll also need a USB 3 compatible port on your PC to take advantage of these faster speeds.
The drawback with USB external disks is that they need to be connected directly to a computer making it complicated to make the additional disk available to multiple computers accross a network.
NAS devices offer the ability to plug additional disk (storage) directly into your computer network making it completely independent and available to multiple resources simultaneously. One of the common uses for this type of storage in business is for backup capacity or for additional low value storage.
It is important to understand the limitations and restraints of a NAS and we constantly field questions from users disappointed with the performance of NAS storage. The reason for this poor performance is often incorrectly diagnosed as a limitation of the speed of the network and the below explains the real reason of the issue.
In our example we had a customer (who we provide support for) question our ability to construct a decent computer network. This was due to the time taken to transfer 400GB of files from his computer to a NAS unit and in their eyes appeared to be excessive. (The Customer purchased the NAS device from a local retail store).
What needs to be understood about NAS devices is that they are basically a “mini computer” which takes network data and writes it to the disk. A NAS has an operating system just like any computer and the majority of NAS’s units use a variant of Linux called “Black Box”. In the same way a desktop computer runs Windows, the more powerful the processor, the faster it can perform its functions.
To explain the problem we need to understand difference between Gb and GB (often confused). Network speed is measure in bits whereas files are measured in Bytes. To convert network speed (bits) to file size (Bytes), we take the network speed divide by 8. This is very important to understand and not confuse when doing these types of calculations.
Looking at the theoretical possible data transfer speed of a standard 1Gb (1000 MB) network of today, the math looks something like this.
Firstly to convert Mb/s (network transfer speed) to MB/s (file size)
1000Mb/s divided by 8 = 125MB/second
This is the size of file that can be transferred in a second, so this is telling us that we can transfer a file of 125MB per Second across a 1Gb network.
Converting per second file transfer to per minute.
125MB/s x 60 = 7500 or (7.5GB) per minute size file that can be transferred
Converting per minute transfer to per hour
7500MB/s x 60 = 450000 or (450GB per hour)
So the above calculations tell us on a Gigabit network we should be able transfer a file of 450 Gigi Bytes in one hour. If my customer could get the theoretical maximum throughput they should be able to transfer their file in less than an hour.
*******Please remember this is theoretical only********
Now let’s look at some real world calculations….
The first thing we have to do in to get the brand and model of the NAS that you intend to use and find true throughput figures for the hardware. This you need to be a little careful as we have found that going to the manufactures web site is the LAST place you will get accurate information from. We choose to visit respected hardware reviewers website “Toms Hardware” and found the below graphic.
Looking at above we can see that the clients NAS is capable of around 19MBs (you need to be very careful of the “B”, is it a small “b” = megabits or a capital “B” = megabytes. In this case it is a capital “B”.
So 20MB = 160Mbs (even though the NAS has a Gb interface). This clearly shows the network traffic from or to this NAS would be 1/8th of the available network throughput showing clearly that the bottleneck is NOT the network connection.
Continuing with the math on my customer’s network;
20MBs (Customers NAS Performance) x 60 seconds = 1200MB or 1.2GB per Minute (File size)
1.2 x 60 minutes = 72GB data per hour of NAS transfer capability.
If the customer (as in our case) is transferring 400GB of data;
400GB divided by 72GB = 5.5Hours hours to transfer the customer’s data….
So the question then becomes how can do to reduce the time to transfer this data?
The answer to this question is to ensure that the NAS that you select has the capability to transfer data at the speed you expect to satisfy your needs. To put this in perspective, we tend to recommend either QNAP or Synology NAS units. (Industry recognised as the leading NAS manufacturers).
To purchase a low end unpopulated (No drives installed) 4 Bay 20MB/s NAS is around $550NZ. These lower end units tend to only be capable of around 20MB/s.
To purchase what looks from physical appearance to be the same NAS with a higher end processor with around 80 or 90MB/s throughput is around $1700NZ (3 times the price of the lower cost unit) without any installed drives.
Logical Solutions have developed a solution based on industry best of breed (HP) equipment and at a very similar price point to that of the low end NAS solution with configure-ability and performance greater than the higher end NAS units. Our customers are very impressed with the solution and finding in many cases it out preforms many of the mid to higher end servers without any “got-ya licensing restrictions they have experienced in the past. Please contact our offices to find out more information on this exciting product.
I hope this helps you understand some of the pitfalls that need to be considered when purchasing Network Attached Storage (NAS) appliances and the old adage that there are no free lunches in this world, you get what you pay for…