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New Member

write accelaration and how it works

can someone give more details about how write accelaration works and improvements. The advantages and disadvantages of it pls?

5 REPLIES
New Member

Re: write accelaration and how it works

The write acceleration improves the application performance of routed traffic in FCIP tunnel.

The main idea is to minimize the WAN latency based on the received acknowledgments. With this option enabled you minimize the round trip transfers (RTT) or said with simple worlds, the "transfer ready" value. This acknowledgment are simulated between the local switches, instead waiting the answer from the remote one.

Regards,

Jordan

New Member

Re: write accelaration and how it works

Thank You, I found another useful white paper(Attached). we are implementing write accelaration between our primary and secondary data centers and wanted to avoid potential pitfalls. I dont see anything for that though.

Cisco Employee

Re: write accelaration and how it works

Write acceleration responds locally to the transfer_ready SCSI command rather than let it flow all the way across the FCIP link and then back. The transfer_ready command precipitates a flow of write SCSI commands, so by responding to it locally, the actual data gets flowing faster. After acknowledging the Xfer_Rdy, the MDS's then buffer it and send it across to get the acknowledgement. The end devices don't know it is the MDS's that are in the middle taking care of this. The key is that the initiating device is able to get the write commands out faster. The caveat to WA is that the link bounces when you add it to the configuration. Also, it is important to check which replication methods have been certified. For example, SRDF benefits from WA but SANCopy does not.

New Member

Re: write accelaration and how it works

Can you please elaborate as to why SAN Copy dooes not benifit from FC-WA.

Cisco Employee

Re: write accelaration and how it works

It was my mistake. SANCopy does benefit from FCWA

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