A Viable Alternative to Xsan: Gigabit and 10GbE Ethernet

Most work groups that have a Mac network based environment are familiar with Xsan. If you're not, you may know someone who works with one, or you may be like a lot of other current or potential Mac users and considering installing it. As the demand for Storage Area Networks (SAN) continue to rise, I encourage you to look around as always and consider your best option for your next IT update.

A little about Xsan, what it is, and what it can do for you.

The idea behind Xsan is to allow multiple computers to concurrently access terabytes or even petabytes of storage data information on Apple's Xserve RAID over a high-speed Fibre Channel network. This also means that you need a very good network configuration to make it go off without a hitch. Here are several things that Xsan can do for you.

1. Entire groups of users in an organization can share files and disk volumes sizes up to two petabytes (2PB). That's huge!
2. Windows and Linux workstations can connect to Xsan together. Yes!
3. With Xsan your not just stuck at just a single workstation. Instead, you can work from any work station connected to the storage area network (SAN). You can be mobile inside your building facility!
4. Apple's Xsan does away with wasted space from duplicated copies of the media. You can get more use out of your storage network. It's under one big storage rooftop!
5. Nothing beats Fibre Channel for performance and value. Xsan takes advantage of those precious speeds. Fibre Channel is certainly fast!
6. All of the systems on the storage network can read and write to shared storage simultaneously, unlike other vendor solutions which gate access at the volume level is generally speaking of what you get.

So now, what about cost?

Get your calculators please. Assuming that you have already invested in an Xserve RAID ($8,000.00 - $15,000.00). You'll also need an Apple Xsan certified Fibre Channel switch, so go with a certified partner switch ($4,000.00 - $9,000.00). Oh yea, you also need to have a Meta Data sever, so, throw in another thousand or two for that. Now, let's assume you have the common (3) clients that you want to use for Xsan. Now, you will be required to buy a client license for each node which respectively retails for about $999.00 per node. In this case that comes to around $3,000.00 for software (in this case, do your own requirement).

Some more Xsan interesting facts...

* The costs per node (client) happens every time you want to put another system on the Xsan network. You need to buy another license every time. That could be a big downfall for a quickly expanding company!

* Xsan requires you to use an Apple Consultant / Apple Specialist to do the install. This will lead you to even more overhead costs of getting the equipment installed and managed by someone who knows how to manage an Xsan configuration.

* A lot of Fibre Channel switches do not scale well. So, if you have a large port count and you need more then what your small current Fiber Channel switch can handle, you will more then likely be forced to buy a new Fibre Channel switch with more port counts which is going to cost some good mullah!

* Xserve RAID is not really "fast" in terms of what most other vendors have. They only do roughly about 180 MB/sec. What that means for you the user is that on a 180MB file it will take about one second to retrieve it from the disk. On a RAID that's 3 x that speed it's about 1/3 of the time. Oh yea! It cannot take advantage of the full 4GB Fibre Channel speeds yet either!

With that said and all things considered, you can get into an Xsan for less then $30,000 in a small workgroup environment. Most of the installs I hear about are more like $50,000 to $75,000 and up.

Assuming the above and figuring the smallest dollar figures from above, your cost for an Xsan implementation is around $15,000 which comes out to $5,000.00 per client, roughly.

Here are some various Xsan Configuration Diagrams (http://www.xsanity.com/mediagallery/album.php?aid=2&sort=0&page=1). You will be able to get a good idea of their complexity with even the smallest of configurations.

Now, a viable alternative to Xsan.

It's Gigabit Ethernet. It's also 10Gb Ethernet for those low latency high bandwidth application requirements.

Chances are, you already have most all of what you need in place to take advantage and give yourself an "Xsan like environment". Although Ethernet does not perform the same as Fibre Channel would, it's still possible to configure such a set up that you could get close "Fibre Channel like" results. Let me explain.

When compared to Xsan, Gigabit is not an out performer by any means, but it is much less cost and can provide similar performance. There are other things that can be done to get better performance with the way this is configured. Also, having the infrastructure in place already is an added bonus because you can utilize your pre-existing IT resources to do all of the configuration and set up work on your own without the expensive overhead of consultants.

Let's assume the same scenario as above with our client considering Xsan, only this time, we use Gigabit options from Small Tree.

Again we'll assume you've already invested in some kind of RAID or Direct Attached Storage. However, now, instead of a Fibre Channel switch you will want a good managed gigabit switch. I recommend Small Tree's ES4524D from Edge-corE ($2,000.00). Because you're not going with Xsan, you don't require the need for a Meta Data Server now. Let's continue assuming you have the common (3) clients that you wanted to use for Xsan but now, we will use Gigabit network cards in these.

We recommend having two available Ethernet ports on your clients because what you want to do is set them up on a Jumbo Frame network to give your Video Editors their own dedicated network separate from the "administrative" network where you do email, web surfing, etc ... You will still be using one of the three for a server. Count on 2 Single Port Gigabit network cards ($179.00 each) and 1 Dual Port ($329.00).

If you get into an environment where you have a lot of clients, you should take advantage of a Quad or Six port Server Gigabit cards to give you the proper bandwidth you need into the Server. In this case where we have only 3 clients, A single or a dual port card would suffice, because we will link aggregate the card to the built in ethernet ports on the Mac to achieve our access from Server to switch.

What do you need to do to implement this above Gigabit configuration?

1. Install a Small Tree Gigabit network card into your Server. (Mac, Windows, and Linux)
2. Install a Small Tree Managed Switch with Dynamic Link Aggregation support.
3. Install Small Tree Gigabit network cards into your clients. (Mac, Windows, and Linux)
4. Set up Link Aggregation on the server.
5. Set up Link Aggregation on the switch.
6. Turn on Jumbo Frames at each of your clients.
7. Give each of the client's their connections to the appropriate networks. (Jumbo Frame / Administrative)

Doing a similar estimate for Gigabit like we did above for Xsan your implementation costs are around $2,700.00 which comes out to $900.00 per client, roughly.

Here is a before and after of what you can expect to see with this kind configuration.