Performance SANs are there to provide optimal performance for mission critical workloads and need to be managed as a whole. The switches and storage arrays that comprise the SAN each have data collection capabilities but do not provide an end-to-end view. The most logical and cost-effective place to tap into the key performance data of a SAN is just before the storage ports. Wikibon recommends that performance SANs be enabled to collect end-to-end performance data by putting in splitters between the storage array ports and the rest of the SAN. Splitters(or TAPs, Traffic Access Points) are passive devices that take a percentage of the light from a fibre cable that can be connected to performance data analyzers. The cost is approximately $300 per storage port and should be built in to the purchase and operating procedures for all performance SANs.
The steps to fitting splitters are:
- Determine if multi-pathing has been correctly set up for each port, and ensure that any fail-over infrastructure that should have been there is actually there!
- Retrofit splitters/TAPs to all existing storage ports (non-disruptive if step 1 housecleaning has been done).
- Set in place purchase and installation procedures and training to ensure that splitters are installed as standard with every new array.
In the 1/12/2010 Peer Incite, Ryan Perkowski talked about the importance of choosing best-of-breed tools for the SAN as a whole. For the end-to-end performance analyzer, he chose Virtual Instruments, which provides the NetWisdom probes that record and store all the data from the splitters and other SAN components, and enable this data to be analyzed and correlated. For overall SAN management, he chose the SANScreen product from NetApp, and for array management he chose the tools from the array vendor.
Action Item: Senior IT management should identify the performance SAN infrastructure, ensure that effective end-to-end SAN performance tools are enabled by putting in fibre splitters as standard, and use best-of-breed end-to-end SAN performance tools to manage SAN performance.