Low speed effects on Fibre Channel Devices
Posted by Sven Koester, Last modified by Sven Koester on 17 April 2012 12:01
It has been reported to our hotline that some speed loss effects may arise on fibre channel architectures, namely this arose with Sun Solaris hosts. The result is extremely low data transmission speed.
This effect is often caused by repeated speed negotiation of multiple devices in the fibre channel. Namely some 4 GB/s devices tend to re-negotiate the speed on the channel. Due to that, the speed on the fibre channel may reduce drastically.

This behaviour is non deterministic, so there is no clearly identifyable fault. The following changes solved the problem in some cases:
- Reduce the speed from 4 GB/s to 2 GB/s (if applicable)
- Do not allow automatic speed detection but set a fixed speed for each device
- Try to exchange the FC host adapter against a diffferent manufaturer's adapter.

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