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Very slow client backup


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My backup server, RWS8, is a P4 2.4ghz box with 1GB RAM and 3x70GB and 2x160GB Maxtor drives, XP Home Edition.


One client, RWS15, is an Intel P3/850 mhz, 640MB RAM, 2x30GB Maxtors, Windows 2000.


Another client, RWS3, is an IBM Thinkad T41, 1.3ghz, 512MB RAM, 60GB disk, XP Professional.


The backup sets are on RWS8's 2x160GB drives, DMA6, 7200RPM.


All computers are networked on one segment at 100mb/sec full-duplex.


When I back up RWS8 to RWS8 it FLIES at 1800MB/min.


When I back up RWS15 to RWS8 over the network I get about 1000mb/min.


When I back up RWS3 to RWS8 over the network I get about 80MB/min.


Any ideas as to why RWS3->RWS8 is so slow? Is XP Pro my problem?

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OK. I solved my own problem...


I installed Etheral from http://www.ethereal.com and used it to discover that I had a lot of retransmissions when sending data between the Server and a Client. Each was set to 100MB FDX, running through a 10/100 switch, and I was seeing about 0.33% LAN utilization. I next dropped the speed of the Server NIC to 10MB FDX and the LAN utilization jumped UP to 98% (of 10MB/sec). So I went from 330,000 bits/second to 9,800,000 by lowering the link speed from 100MB down to 10MB. (There's a message here!)


I next unplugged the Server and Client from the intervening switch and linked them directly together with a Crossover Cable and set the Server and Client back to 100MB FDX again. In this configuration I got 80% LAN utilization, 80,000,000 bits/second.


This lead me to suspect the switch was bad so I swapped in a new switch and had the same poor performance, thus eliminating the switch as the source of the problem.


What this all told me was that the only common thing left was the original cable. I checked that is was CAT5/UTP and replaced it with another CAT5/UTP.


Voila! I now get 80,000,000 through the switch.


The lesson: If you have a lot of retransmissions, try a new cable on the Server and the Client. It may work fine at 10MB and fail at 100MB.



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