Implementing Fibre Channel SANs in a virtual server environment

Eric Siebert discusses the pros and cons of implementing Fibre Channel SANs in a virtual server environment in this interview.

Fibre Channel (FC) SANs are a popular choice for virtual server environments. They offer good performance and security, and since many people already have Fibre Channel SANs implemented in their environment, they often stick with the same technology for the virtual environments. However, Fibre Channel SANs are not right for everyone's virtual server platforms. They are expensive, and also require experienced administrators to implement them.

In this podcast interview, Eric Siebert, a VMwareexpert and author of two books on virtualization, discusses FC SANs for virtual server environments. Learn about the advantages and disadvantages of implementing FC SANs to support your virtual server platform, what steps to take to set up a Fibre Channel SAN correctly and what requirements you should know before you choose a Fibre Channel SAN. Read his transcript below or download the MP3 recording.

Listen to the Fibre Channel SANs Q&A.

Fibre Channel is a popular choice when it comes to virtual server environments--What are the benefits of using Fibre Channel SANS to support a virtual server platform?

Eric Siebert: Typically Fibre Channel is one of the best performing and most secure of the storage technologies that are available today, so people go for that because they want the performance and requirements that they really need and the most possible I/Os they can get . Fibre Channel has traditionally always been what they would implement to get that performance and security standpoint. Fibre Channel networks are all hopefully isolated and kept on their own separate environments, so they are more secure than traditional and other types of networks like iSCSI.

Fibre Channel is also commonly deployed in the enterprise storage architecture, so a lot of people have Fibre Channel SANs already that they can leverage. So in a lot of cases, rather than having to implement something from scratch, they already have a Fibre Channel SAN available that they could maybe expand on.

Fibre Channel storage also has a block-level storage that can be used on other storage devices like NFS or file-level storage. And if you wanted to other things like boot from SAN, Fibre Channel SANs already have those features, and they're starting to become available in some of the other technologies as well, such as iSCSI, where you can boot from SAN and have a headless server. So you don't have to put disks in the server; it can just boot directly from the SAN and run from a VM environment.

What disadvantages or complications can you run into with FC SANs for a virtual server environment?

Siebert: There are two big ones: cost and complexity. Typically Fibre Channel SANs are the most expensive option available, so if you're looking to implement one from scratch it's really expensive because you have to buy all these expensive different components that are made specifically for Fibre Channel: Fibre Channel cables, Fibre Channel adapters that you have to put in your servers, switches and backend SAN storage, so the cost would be pretty high. The reason it is so high is because of the performance – the cost is relative to that – you're going to have to pay a lot more money to get that performance, so cost is one of the major disadvantages of that.

In terms of complexity, Fibre Channel SANs typically require specialized skill sets where your average server administrator wouldn't have those skills to be able to administer it properly. Typically you need a specialized skill, and you need an administrator who really understands the technology and can implement it properly.

How do you set up a FC storage device to support virtual servers? What steps do you need to do to ensure everything runs smoothly?

Siebert: It's pretty straight forward. You just have to be aware of things like speeds. There are different types of speeds for Fibre Channel, but typically today the most common one to use is 4 GB. The newer ones are 8 GB, which provide double the speed. You don't want to mix components; you want to have the disk that's going to run at the lowest speed. So if you have a 2 GB or 1 GB card as your server, your switches are 4 GB or 8 GB and so is your backend storage, plus it's only going to operate on the lowest common speed denominator, so you want to make sure that you have all your components at the same speed to get the most value and speed out of your environment.

Also consider things like multipathing. You want to make sure you have redundancies so typically you would implement a multipath to a SAN, so it's all the way from the server where you would have two Fibre Channel adapters inside the server, switches, and then typically there are two controllers on the Fibre Channel SAN, so if any one component breaks you should always open a path to get to from the server to the SAN. If you implement multi-pathing and also using other technologies like active-active where both paths are active, you can get more performance out of it that way. That's always a good idea to keep in mind when you're implementing a Fibre Channel SAN.

Overall, setting up a Fibre Channel SAN can be complicated, so typically you should make sure everything is set up properly and is working properly. Proper preparation is key for proper configuration. And work closely with your SAN and storage administrators; make sure they understand your needs.

Are there any requirements you need to know about before choosing an FC SAN? Does this storage option require more experienced administrators?

Siebert: Yes requirements are the key here. You need to know your requirements. If you have applications that need a specific amount of I/O, you need to know what that is to be able to size your SAN properly. You shouldn't go in there blind and assume that just because Fibre Channel SAN is going to be fast that it will work for you. You really need to go out and do the homework. Do an assessment of your environment, figure out what your I/O requirements are, if you have any type of redundancy requirements, and then figure out capacity as well. You need to know how much storage you need to buy for that Fibre Channel SAN to see if it has the capacity for all of your virtual machines.

Other requirements to consider are things like the features you need. There might be certain features you might want to implement on that SAN such as snapshot capabilities and replication. Also, if you have a disaster recovery strategy, you want to make sure you include your needs for that because a lot of time you can be leveraging storage features to move from your main site to an alternate DR site. So you really need to assess your requirements and what kind of features and functionalities you're going to need before you go out and buy one.

Also there are some new features for VMware like the vStorage APIs – there are certain feature sets that they have that a lot of SANs are supporting now. The vStorage APIs for array integration will offload some of the storage paths that traditionally some of the hypervisors would do to the storage layer to make it a lot quicker, and so you can take a load off of your virtualization and put it on the storage infrastructure and that will improve the performance of your virtual host as well as the task on the storage device where it should be, and that makes it a lot more efficient.

So basically you want to look around, evaluate, ask questions, get references, get your requirements and go from there and make a decision and hopefully you can find the right Fibre Channel solution that meets your needs.

This was last published in April 2011

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