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Message Posted: Wed, 30 Jul 2003 @ 19:24:07 GMT


     
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Subj:   ARCMAIN and STK 9840 Drives
 
From:   Harold D Kleven

We're experiencing a performance problem trying to backup to STK9840 drives via ARCMAIN on MVS. Several tests and NCR's analysis seem to indicate that we're only able to drive the tapes at approx 4.5MB/sec. The tapes are able to support 10MB/sec - and higher speeds at burst. Test statistics at all levels have shown that the server (a 12node 5350) is loafing along and the channels are not stressed and it's the ARCMAIN where all the time is being used. The TDP has plenty of buffers and there is no wait for new allocations, etc. NCR indicated that the problem may be in the way ARCMAIN handles IO (asyncronous) and the "streaming" nature of the tape drive results in "temporary write errors" causing so much logical and mechanical correction activity by the drive that we're only able to get 4.5 as an effective rate.

Has anyone else experienced/heard of this problem before? We're wondering if it's simply a problem at our site - a "soft" problem that we could overcome - or an actual "hard" problem that can't be overcome.



     
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