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Hi Andy and Wilko, Thanks for the clarification. I wasn't sure if the kXR_wait was an indication of an error condition or was normal. Patrick Andrew Hanushevsky wrote: > Hi Patrick, > > By default, the redirector asks the client to wait 5 second when it > encounters a file it has never seen before. The reason is to give > sufficient time for all the data servers to indicate whether they > already have the file. This is a standard tactic in a large distributed > cluster where there is no single point of control. Can we do better? > Perhaps, we can give the option of allowing a client saying "I don't > care" give me a destination server right away. > > Now, the easier way to get around this philisophical problem is to issue > a "prepare" request for all the files you want to load. This request > happens in parallel and then when you really want to load the files, the > redirector knows what is there and what is not. In practice, it means > you suffer the 5 seconds delay only once. > > The only thing I can say is that xrootd does not behave as a standard > filesystem (which most people are used to). On the other hand, because > it does not, it can give you much better performance in the standard > case (i.e., sub-millisecond response time for existent file opens). > > Andy > > On Sat, 8 Dec 2007, Patrick McGuigan wrote: > >> I have a basic system working with one client, seven dataservers, and >> a redirector. The client can store correctly but I am observing a >> consistent five second delay when the client is storing data. >> >> I ran xrdcp with -d 3 and the output contains : >> >> 071207 23:03:40 001 Xrd: DoLogin: No prev session info for >> 10.1.2.255:1094 >> 071207 23:03:40 001 Xrd: Open: Access to server granted. >> 071207 23:03:40 001 Xrd: Open: Opening the remote file /xrd/test24/100mb >> 071207 23:03:40 001 Xrd: Open: File open in progress. >> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: Reading header >> (8 bytes). >> 071207 23:03:40 18805 Xrd: ReadRaw: Reading from 10.1.2.255:1094 >> 071207 23:03:40 18805 Xrd: SendGenCommand: Sending command Open >> 071207 23:03:40 18805 Xrd: WriteRaw: Writing 24 bytes to physical >> connection >> 071207 23:03:40 18805 Xrd: WriteRaw: Writing to substreamid 0 >> 071207 23:03:40 18805 Xrd: WriteRaw: Writing 17 bytes to physical >> connection >> 071207 23:03:40 18805 Xrd: WriteRaw: Writing to substreamid 0 >> 071207 23:03:40 18805 Xrd: ReadPartialAnswer: Reading a >> XrdClientMessage from the server [10.1.2.255:1094]... >> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: sid: 1, IsAttn: >> 0, substreamid: 0 >> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: Reading data (4 >> bytes) from substream 0 >> 071207 23:03:40 18805 Xrd: ReadRaw: Reading from 10.1.2.255:1094 >> 071207 23:03:40 18805 Xrd: BuildMessage: posting id 1 >> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: Reading header >> (8 bytes). >> 071207 23:03:40 18805 Xrd: ReadRaw: Reading from 10.1.2.255:1094 >> 071207 23:03:40 18805 Xrd: ReadPartialAnswer: Server [10.1.2.255:1094] >> answered [kXR_wait] (4005) >> 071207 23:03:40 18805 Xrd: CheckErrorStatus: Server [10.1.2.255:1094] >> requested 5 seconds of wait >> 071207 23:03:42 18805 Xrd: DumpPhyConn: Phyconn entry, >> [log in to unmask]:1094', LogCnt=1 Valid >> 071207 23:03:44 18805 Xrd: DumpPhyConn: Phyconn entry, >> [log in to unmask]:1094', LogCnt=1 Valid >> 071207 23:03:45 18805 Xrd: SendGenCommand: Sending command Open >> >> >> >> It appears that the client received a 5 second delay from the >> redirector. I don't seen any useful information in the olbd log of >> the redirector and the xrootd log only indicates that the client was >> asked to wait: >> >> 071207 22:54:24 15092 odc_send2Man: root.18805:16@compute-0-0 asked to >> wait 5 by xrdb path=/xrd/test24/100mb >> >> >> How do I determine why the redirector is sending xXR_wait? >> >> Is the result of my configuration defaulting to round robin scheduling? >> >> >> Thanks, >> >> Patrick >> >> >> >> >> >> >>