We are backing up a 270c nightly with Netbackup via NDMP to a dual drive LTO3 machine (only one drive is used for to backup the filer). There are 2.25 TB on one head and 1.1TB on the other. For a full backup it takes about 10 hours to write to tape, which I don't think is too bad (larger volumes hit 31200 KB/sec reported by Netbackup), but the differentials take 5 hours to run,even though the delta on our data is very small.

I suspect this is more of a Netbackup issue then a filer based one but wanted to throw it out there incase there was something I should look at on the host side. This is over a normal gigE switched network connection with the default settings on the filer, network-wise. We are not using virtual interfaces, both heads have a single 1 gig connection to the LAN. Any suggestions or inventive flames are welcome.

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