What you'll learn in this tip: Storage performance issues are often linked to storage networks with outdated information or that aren't regularly tested. Follow these five tips to improve your performance and
avoid bottlenecks in your storage networks.
Storage networks require constant maintenance and attention. If there's a lull in your storage environment when you aren't working on repairs or recovering from a disaster, it's not necessarily a time for you to sit back and relax. These calm moments should be spent improving your storage networks and ironing out any kinks you might have in preparation for the next disaster or repair.
These five tips will help you improve your storage-area networks (SANs) and fine-tune your storage networks. Find out what steps you should take to prepare your SAN for the worst, and learn what you can do to improve your storage network performance, efficiency and resiliency.
Tip 1. Know what you have in your storage network
The first and most important step is to understand what you have in your data storage environment. Make sure you have an updated inventory of your networking environment at all times. If you should need to bring in a vendor's tech expert, they'll ask for one. Having an accurate and up-to-date inventory means you may not have to pay as much for professional services, and may even avoid having to call for help in the first place.
It's crucial to document every host bus adapter (HBA), cable and switch. Note how they're interconnected, the speeds they're set at, and the software or drivers they're running. Although these tasks seem obvious and mundane, they're often overlooked and knocked off priority lists during a typical work day. It's incredibly important to take time out from your day to understand what is in your environment.
More importantly, recording this information often highlights areas that need improvement. For example, there have been cases where users upgraded to 4 GB Fibre Channel (FC), but their inter-switch links (ISLs) are still set at 1 GB. If they had taken the time to document these changes, they could have had doubled their performance much earlier.
Keep in mind that you don't have to track these changes manually. Although tasks like these could cost nothing if you do them in a spreadsheet, many vendors sell software and hardware tools that can track this information automatically. If you're worried about the price of these storage resource management (SRM) tools, you shouldn't. They can be a good investment, especially if these things might fall to the wayside otherwise. Plus, they vary in cost and complexity. You can choose a simple SRM tool that polls devices and records status data, or a more complex one that analyzes the network frames.
Tip 2. Know what's going on in your storage network infrastructure
After you've developed a good picture of the components in your storage network infrastructure, the next step is to fully understand what those devices are doing at a particular moment in time. Many switch and HBA vendors build some of these capabilities into their products. But instead of going to each device to see its view of traffic conditions, it may be better to find a tool that can provide consolidated real-time feedback on how data is traversing your network. There are software solutions and physical layer access tools that can report on the infrastructure traffic. The tools that can monitor network devices specifically are important because there are situations where operating systems or applications report inaccurate information when compared to what the device is reporting.
These tools can be used for trend analysis and, in some cases, they can simulate an upcoming occurrence of a data storage infrastructure problem. For example, if an ISL is seeing a steady increase in traffic, the ability to trend that traffic growth will help identify how soon an application rebalance or an increase in ISL bandwidth will be required. Other tools will report on CRC or packet errors to ports, which can indicate an upcoming SFP failure.
Tip 3. Know what you want to do
With your inventory complete and good visibility into your SAN established, the next step is to figure out what network changes will provide the most benefit to the organization. You may have discovered SAN features that need to be enabled, or perhaps you have new applications or an accelerated rollout of current initiatives that need to be planned. Knowing how activities such as those will impact the rest of the environment and what role the storage infrastructure has to play in those tasks is critical. Generally, the goals come down to increasing reliability or performance, but they may also be to reduce costs.
Tip 4. Limit the impact
When you feel you're at the stage where you're ready to make changes to the environment, the next step is to limit the sphere of impact as much as possible by subdividing the SAN into virtual SANs (VSANs).
Subdividing (in a worst-case scenario) changes made to the environment that yield unexpected results, like preventing a server from accessing storage or even causing an outage, will have limited repercussions across the infrastructure. Limiting the sphere of impact is by itself an important fine-tuning step that will help create an environment that's more resilient to changes in the future, and can help contain problems. For example, an application may suddenly need an excessive amount of storage resources; subdividing the SAN will help contain it and keep the rest of the infrastructure from being starved. This aspect of fine-tuning shouldn't require any new purchases as it's a setup and configuration process.
Tip 5. Test to learn, learn to test
Although it may seem to be something of a luxury, one key to fine-tuning is to have a permanent testing lab that can be used to try out proposed changes to the environment or to simulate failed conditions. Lab testing lets you explore the alternatives and develop remedies without impacting the production network. In speaking with our experts, and in our own experience, most SAN emergencies result from implementing a new feature in the storage array or on the SAN. If you lack the resources to create a lab environment, an alternative may be to work with your infrastructure vendors, as many have facilities that can be used to recreate problems or to test the implementation of new features.
These five tips will help you avoid a lot of storage I/O performance issues you might otherwise encounter in your data storage environments. Knowing what you have in your storage networks, keeping track of what's going on in them, and planning and testing your environment will identify problems and snags that might otherwise go unnoticed.
BIO: George Crump is president and founder of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments.
This article originally appeared in Storage
This was first published in February 2011