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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: Symmetric vs Asymmetric1) I don't like the asymmetric model because when solving the synchronization of the commands by sending the commands on a same TCP connexion, it just moves the synchronization problem in an other place : how to synchronize the commands and their data (pb described but Matt and Somesh). 2)The advantage of the asymmetric model (when two connections at least): "avoid the problem of commands flow controlled by large transfer of data" is not an advantage compared to the symmetric model. Because to do so the asymmetric model needs at least two connections. In this case, the symmetric model could avoid this problem too : - opening two TCP connections one for the normal command (read/write,...) and a second one for the urgent commands (task management etc...) 3) As stated it seems that we needs a flow control of the commands because if we use the SCSI one (TASK SET FULL) the traffic we will instable and composed of a sequence of bursts with regularly a full RoundTripTime*Throughput/size of a command number of commands to retry. The command window in the iSCSI draft seems not to be a good mechanism to flow control the commands, because if there is a mix of slow and fast commands, the result will be a task set half full but a window closed, hence the traffic blocked. Why not replace in the draft the "MAXCmdRN" by a credit that is a number of commands in flight allowed (not yet completed) independent of the "CmdRN"? Doing that, the flow will not be blocked by a slow command but will blocked only upon the filling of the task set. Pierre
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