Write speed to "local" network storage


OSNN Newbie
7 Feb 2005

I have what I believe to be a network issue. Background info:

I record tv onto a "video server" in my basement using a program called Sagetv. I have two other pc's in my home that act as Sagetv clients and play back .mpeg files stored on the server. There is a utility known as comskip (ie commercial skipping) that can be used with Sagetv. Comskip runs on the server (where the files are located) and generates .edl files that the client uses to skip over commercials during playback. In order for this to work the portion of the comskip utility that runs on the clients needs to access the video files using the same path that the server uses. This can be done by using UNC paths for the HDD's that store the recordings and .edl files.

There are four capture devices the server uses to capture the video files. Two of the devices are VBox usb tunners that receive high def over the air tv broadcasts and two of the devices are ATI TV Wonder TheaterPro 650 pci cards. The pci cards receiver audio and video via SVideo and Stereo connections from two Directv receivers. The ATI cards are hardware encoders, so there is little to no cpu overhead when using them. All these tuners write .mpeg files to the HDD's.

My problem lies in trying to watch "live" tv. When watching live tv using Sagetv the tuner sends the .mpeg file to the HDD and then sage plays it back. Obviously, this is not really live. You are simply watching a recording immediately after it is made. When I watch "live" tv encoded by one of the VBox usb tuners I have no problems. When I watch "live" tv encoded by one of the pci tuners everything just freezes after a few seconds. If I watch these recordings after they have completed they will play back just fine.

What I am wondering is if this has to do with the UNC pathed drives essentially being "local" network storage. I did a little searching and came up with this regarding writing to a local UNC path:

With the UNC name, your computer will actually ...

With the UNC name, your computer will actually query DNS for the ip of itself, unless that info is in the computers cache. Then it probably moves data to the pci bus and then to the disk controller. The extra copy time is because it thinks its moving it across a network connection so is probably buffering the sent packets.

Is this plausible? If so is there any way I can manipulate the buffering in an effort to increase the write speed?

As for the DNS ip query I was advised to make entries to the server's host file to eliminate this. I had not even heard of the host file before but found a good bit on google. Would I need to do anything beyond ensuring that the localhost is in the file?

I don't know if it matters, but the drives the .mpeg files are stored on are a Raid1 array on a 3Ware 9500S-12 controller card. Now that I think about it, write caching is enabled on the 3Ware card. Would that matter?

The pc in question is based on an intel D865perlk mobo with a P4 3.0e and a gig of ram. OS is Win XP Sp2 fully updated.

Sorry to be long winded. Thanks in advance for any help.


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