Friday 12 September 2008

FC Distance extension solution

In most of the cases customers may need to connect the fibre channel switches at disparate distance. This is mainly to protect the critical data and provide continuous access to data in the event of site disaster.
Normaly while designing a disaster recovery solution two things are taken into consideration - RPO and RTO.
RPO is the acceptable data that a customer can lose in the event of disaster. For eg: if customer is doing a midnight back and if there is a disaster at 10 AM, then 10 hours of data is lost, so in this case RPO is 10 hr.
RTO is the acceptable length of time a break in connectivity can occur with minimal or no impact to customers business.


There are different distance extension solutions

Connecting over dark Fibre : In this case the fibre channel switches are connected using dark fibre. For this a long wave SFP is used. Additional license is required to configure buffer to buffer credit for the ports involved so that latency imposed by distance can be avoided. Distance upto 100km is acheived.


DWDM/TDM : Another method of extending fabric is by using DWDM or TDM equipment. In this case switch port is connected to the equipment for extending the fabric. Using this fiber distances between nodes can generally extend up to 100 km or farther

FCIP: Fibre Channel over IP (FCIP) enables to connect Fibre Channel SANs over IP-based networks.
This need FCIP blades to encapsulate fibre channel frames within IP frames and sent it over IP network to the peer switch. When the IP packets are received at other end, the fibre channel frames are reconstructed.
Some of  the brocade models that support FCIP - MP-7500B switches, PB-48K-18i blades.
Cisco models that support FCIP -MDS 9200(9222i), 9216i and MDS 9500 series switches support FCIP, using the IPS-8, IPS-4 and the 14+2 blades