Why is my backup rate less than 25 MB/min over the network?

Slow throughput of a filesystem backup over the network is a common problem.
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Please understand that it is not unusual to see slow throughput of Exchange backups over the network; this FAQ is for troubleshooting filesystem backups, not Exchange or SQL.
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The most common problem that causes slow network backups (<25 MB/min) of filesystems is incorrect networking configuration.
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Ethernet hardware switch and NIC manufactures would have you believe that features such as "full-duplex" and "auto-detect" are fully supported in every environment. This widespread belief is simply not true.
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Another issue is the NIC driver. The NIC driver can be overwritten by a service pack. Do not allow this to happen. If you service pack, apply the correct NIC driver after the service pack has been applied. Always use the certified NIC driver for the release of the OS from the manufacturer website.
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Another common problem is not understanding Compaq hardware. Compaq hardware REQUIRES special updates that go on AFTER the service packs - SSDs. These are Compaq specific hardware drivers for the OS.
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When you configure the hardware settings for the Arcserve server NIC and the NICs for machines being backed up, NEVER use the "autodetect" setting for speed or duplex.
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ALWAYS manually set the speed to 100 Mb and the duplex to HALF for the server side.
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Find out which Ethernet switch port the server is connected to, and MANUALLY set the SWITCH PORT to 100 Mb and HALF DUPLEX. DO NOT USE AUTODETECT FOR DUPLEX OR SPEED. Do this for the Arcserve server switch port, AND ALL switch ports for SERVERS BEING BACKED UP BY ARCSERVE.
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Note that in many cases, YOU MUST "COLD" REBOOT (poweroff) for the new NIC settings to be effective. The driver and OS do not always make you aware of this fact.
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Note that when you use a HUB instead of a SWITCH, FULL-DUPLEX is almost NEVER supported for a hub port. Remember, a HUB is a repeater.
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Both SIDES of the connection MUST agree - IF you HARD SET the SWITCH PORT for 100 half, the NIC for the SERVER MUST be set to 100 half.
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Once you have followed all of these recommendations, make a backup of the network target WITHOUT the Arcserve push agent (through the network, using SMB).
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Now, set the Arcserve server, its switchport, the target server, and its switch port, to 100 FULL-duplex. Cold boot the servers.
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Make another backup of the same system using the same job.
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If the FULL DUPLEX backup is SLOWER than the HALF-DUPLEX backup, FULL DUPLEX IS NOT SUPPORTED for your combination of NIC, driver and switch. You MUST use half-duplex only.
Contact your NIC and SWITCH manufacturer for updated drivers and firmware.
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