Effective problem determination of I/O issues requires knowledge of what was going over the I/O network and when incidents happened. Software instruments can provide some data from I/O network components such as storage arrays and switches. However, as telecom and IP networks have known for years, the only effective was to determine the root cause of complex problems is to be able to sample information going across the I/O network fiber infrastructure directly. Hardware and software probes from companies such as Virtual Instruments then create an ongoing database of the information and enable end-to-end problem determination.
The traditional way to sample the information on the I/O fiber network is to tap[1] the SAN fibers, usually retroactively. This procedure is much more expensive when retro-fitted, both in labor (one to 2 hours per tap) and because the physical connection has to be broken to install the tap. The operation requires careful planning and scheduling.
Virtual Instruments has introduced a new set of capabilities that allow the taps to be put in place when the SAN fiber is installed. Introduced under the SANInsight brand, the taps are provided in cassettes, and up to 48 taps can be put in 1U of rack space.
Action Item: As Fibre Channel (FC) networks increase in bandwidth from 2 to 4, 8, 16 and 40 Gbits/second over the next few years, the ability to tap these fibers will go from nice-to-have to essential. It is 20 times less expensive to install taps as part of the initial FC network than to retrofit them later. Senior IT executives and CTOs should ensure that future SAN fibre networks are specified to specifically include taps. The additional cost (<5%) will be much lower that having to retrofit them later.
Footnotes: Note[1] A tap uses fiber optic splitters to create a mirror copy of the signal from both channels of a duplex link. Taps are passive and transparent to the live data path. Thirty percent of the light is taken for the signal copy. This signal copy is out-of-band and transmit only and has no impact on applications. Taps have been installed as best practice in IP and telecom fiber infrastructure for many years.
