09-12-2005 11:21 AM
can someone give more details about how write accelaration works and improvements. The advantages and disadvantages of it pls?
09-13-2005 01:10 PM
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
09-14-2005 05:54 AM
09-14-2005 07:50 AM
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.
09-16-2005 04:12 AM
Can you please elaborate as to why SAN Copy dooes not benifit from FC-WA.
09-16-2005 05:02 AM
It was my mistake. SANCopy does benefit from FCWA
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