- Bronze, 100 points or more
I was wondering if anyone has used a MDS and ONS 15454 solution to extend the distance limit for HDS sync true copy.
It seems that native fibre has a best practice limit of about 32 km for intensive true copy usage for OLTP. Non intensive supposedly can go up to about 200 km. After that, the latency will cause major problems.
I recall reading somewhere that using DWDM along with the MDS can offer some quite extensive distance expansion to the order of a couple of thousand km's. What I did not see was anything to overcome the latency issue that is there with distance.
I believe the speed of light in fibre is about 5 nanoseconds per metre. So say a 1000 km link would take about 20 milliseconds for the storage cache at both ends to complete the transaction.
So is there any special "thing" available when using the MDS and the ONS to improve the distance by reducing the latency? I know that fibre channel write acceleration is an option but does it overcome the latency issue?