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New Member

true copy over wan with HDS


we are replicating two storage systems HDS9980 with "true copy", the replication is over stm1.

from HDS with uses cisco MDS 9200 to convert FC to GeTH and from there cisco 7600 to convert GeTH to stm1.

we use a full synchronous replication.

my question is , what improvements can we implement: such as jumbo frames , FCIP write acceleration or other suggestions?

New Member

Re: true copy over wan with HDS

Jumbo frame will help performance. But it should be implemented end2end. If you implement true copy sync mode, FCIP write acceleration is not recommended.

New Member

Re: true copy over wan with HDS


what will better improve the performance:

FCIP write acceleration or Jumbo frames?

what mtu size should i choose?

New Member

Re: true copy over wan with HDS

Normally 2300 is big enough for FCP

New Member

Re: true copy over wan with HDS

I found this very interesting as this is something that I intend to do. I have some Tagmastore 1100's that I intend to use to true copy well over 200 odd kilometers and thus use async mode. I am still making my mind up on how to do this. HDS show interesting demo's with using the internet to replicate the data. I purchased the 9509's to make SAN extension all that much easier.. Or at least I hoped it would. Now I have all sorts of options with regards to what to use. SWDM, DWDM, what next. I assume that I can use satellites as latency is not supposedly an issue with async on the HDS and it's buffering abilities.

Life was not meant to be easy.. Any comments?


Cisco Employee

Re: true copy over wan with HDS

From an MDS perspective we can go either FC or FCIP.

200km is not a problem for FC. We have 250 buffer credits standard per port which allows you to go the 200km @ 2Gbps. If you want to use 4 Gbps you will need the extended buffer credit feature which is part of the enterprise license and allows you to define up to 4095 credits per port (more than enough).

For FCIP you can use the write acceleration and hardware compression features.

Portchannelling and VSAN trunking as well as inter-vsan-routing can be used together with QoS mechanisms to optimize the connectivity for both FCIP and FC.

It all depends on how much data needs to get through and what the latency requirements are and what type of connectivity (IP, dark fiber, DWDM) you can get at what price.

You should work with HDS and your local Cisco Storage SE to sort out what is best for you.