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Storage performance issues are often not related to the storage system at all, but rather to the storage network that links servers to disk arrays. These 10 tips will help you find and fix the bottlenecks in your storage network infrastructure.
Every so often there's a moment of calm in a data storage manager's life where nothing is broken and there aren't any fires to put out. As rarely as these times might occur, the momentary calm should be taken advantage of rather than savored. This is your opportunity to get some of the kinks out of your storage network so you can eliminate the next emergency before it happens or just be better prepared when it does. We spoke with experts from storage networking vendors -- Brocade, Cisco, Emulex and Virtual Instruments -- to discuss what storage managers should do to prepare their storage networks for the future and to maximize their investments.
The first few tips that follow have more to do with being prepared than actually tinkering with your storage-area network (SAN), but all of our experts agreed that trying to fine-tune a SAN without adequate preparation is like driving down a freeway without headlights. Before you can roll up your sleeves and get under the hood, you have to do some preparation. The rest of our tips go into more detail, describing specific steps (often at no cost) that you can take to improve SAN performance, efficiency and resiliency.
Tip 1. Know what you have
The No. 1 recommendation in fine-tuning your storage network is to first know what you have in the environment. If you have a problem and need to bring in your vendor's tech experts, the first thing they're going to want is an inventory of your networking environment. If you do the inventory ahead of time, you'll likely pay less for any necessary professional services and it may even help you avoid having to engage them in the first place.
It's important to document each host bus adapter (HBA), cable and switch in the environment while noting how they're interconnected. You should also record the speeds they're actually set at, and the versions of the software or drivers they're running. While all of this may seem painfully obvious, an inventory of what the storage network consists of and how it's configured is the type of document that can quickly fall off the priority list during the urgencies of a typical IT workweek. Taking time to level set and understand what's in the environment, and how it has changed, is critical.
Documenting this information may even pinpoint some areas that are ripe for fine-tuning. We've seen cases where over the course of time users have upgraded to 4 Gb Fibre Channel (FC) and, for some reason, their inter-switch links (ISLs) were still set at 1 Gb. A simple change to the switch configurations effectively doubled their performance. If they hadn't taken the time to do an inventory, this obvious mistake may never have come to light.
This could be a zero-cost tip because the information can be captured and stored in spreadsheets. While manually keeping track of this information is possible, in today's rapidly changing, dynamic data center it's becoming a less practical approach. Storage environments change fast and IT staffs are typically stretched thin, so manually maintaining an infrastructure isn't realistic. Vendors we spoke to, and many others, have software and hardware tools that can capture this information automatically.
Of course, those tools aren't free or as cheap as a spreadsheet. But if you weigh their cost against the cost of manually capturing the data, or the cost of missing an important change to the network environment, it can be a good investment. Automated storage resource management (SRM) tools also vary in the data they capture and the level at which they capture it. Many simply poll devices and record status data, while others tap the physical layer and analyze network frames.
This was first published in September 2010