I'm in the midst of an odd, infuriating problem.  I recently moved from internal drives on a Vista (HomePrem, x32) media center PC and have an odd, very occasional drop/pause in DVD video streamed over the network. I stripped the network back to the VMC PC and the unRaid server, connected via a D-Link DGS2208 gigabit switch with manufactured cables (no home-brew). I disconnected the d-link router as both these boxes have static IPs.

 

I'm getting about 7.5-9.0MB/s when ripping a disc, and 20+MB/s when copying a file _to_ the unRaid server. The network usage is very erratic (large throughput - 30+MB/s, then drops and spikes to average 16-20MB/s)

 

I only get 4-5MB through when reading, and it is a very consistent pattern - 4-5 seconds of 5MB/s, then a drop to zero for a second or so, then back to 5MB...ad infinitum

 

I added my XP laptop to the switch, along with router, to the switch (the lappy gets a dynamic IP). I get the same great, if spikey, transfer _to_ the unRaid box, and a consistent 20-24MB/s _from_ the unraid box (without the regular "drops"). So the server and network appear to be working fine.  A retest of the VMC pc after reconnecting the laptop and router showed identical problems...so it's probably not the presence of the other network stuff.

 

The VMC pc uses a Marvell Yukon 88R8056 (gigabit) on an Abit IP35 motherboard. A sample capture of the network usage in windows task manager is attached. The file is a 1GB VOB file, copied drag&drop to the unRaid box via a share.

 

I realize this isn't necessarily an unRaid problem at this point, but I'm scratching my head as to why (a) I have lousy reads and (b) I have a dropout every 5-7 seconds on this PC. Any suggestions as to what TCP settings - or anything else which - might be bottlenecking only the read side of this conenction?

 

Thanks!

The very first thing to verify is make sure you have Vista Service Pack 1 installed.  It corrects the Vista read issue.  There's a new wiki item on it, not much there yet:  http://lime-technology.com/wiki/index.php?title=Improving_unRAID_Performance#Vista_SP1.  And there have been several threads about it, search the forum for Vista SP1.

 

The jumpiness in writing is well known, as the parity process involves 2 disk reads and 2 disk writes for each single write to the unRAID server, plus there may be a kernel blocking issue that kicks in on receiving large buffers from the network.  Large files incur this 'parity penalty'.  You can get around it by using a Cache drive (Pro version only), see http://lime-technology.com/wiki/index.php?title=Improving_unRAID_Performance#Use_Cache_Drive.

When you're testing your downloads from the unRAID server, are you testing by trying to copy a file to your vista machine or are you testing by trying to play a DVD?

 

I mention this because when trying to play a DVD across your network Vista may buffer the video and won't need to read at 30+MB/sec to play your video. The drop/pause may not be network related... it may be the way you have your media pc configured.

 

Try copying a 2GB file or larger file from your unRAID server to both of your PC's. Record the actual time it took to complete the trasnfer. If the speed is slower on the Vista machine, make sure SP1 is installed as RobJ said. If SP1 is installed, try a 1gigabit NIC and see if that fixes the issue. Your motherboard may have a slow LAN, or the drivers for that LAN aren't working that well with your Vista machine.

Thanks for the replies.  I'm paranoid about changing anything on the vista machine because it is a "production" machine (i.e. the wife a daughter will cry mutiny if it dies) so I have not intentionally installed SP1, though I'll need to check ;-)

 

I'm not worried about max throughput - streaming DVDs and OTA-HD is the largest load it will see.  My issue is that both are having glitches, but they are on a scale larger than most "stuttering" type issues (drops in HD are every 5-10 minutes, drops in DVD only happen every 15 mintues - 1.5 hours). It's pure supposition on my part that the Vitsa media center's read buffer may be running out if one of those drops in throughput occurs at the same time as an extended sequence of fast motion (i.e. high bandwidth).  4MB/s is more than enough for any DVD, and almost enough for 2x ATSC (I use HDhomerun, so I read from the box, write to the unRaid, and read from the unRaid) so it may not be my problem, but I'd like to "correct" it so that it's not a variable. 

 

guitarlp - a 1GB file transfers about 4x as fast on the XP laptop than it does in the Vista machine, and the tests were copying a file, not viewing a DVD. I haven't tried anything larger. The vista machine's onboard lan is supposed to be 1gbps, and it shows as 1gb on the switch and in NetworkMonitor (freeware app), but there could definitely be something wrong with it, or its driver.  If Vista SP! doesn't fix the problem, I'll break out an old, known-good 3com gbit card and load it up to see if it corrects the problem.  Unfortunately, networking is an area in which I've fallen behind in over the last 20 years; sometimes it's hard just to ask the right question any more.

 

Here are a couple of threads, and there are others, concerning read speed on Vista, before installing SP1.  They were generally getting 3 - 6MB/s.

  http://lime-technology.com/forum/index.php?topic=1162.0

  http://lime-technology.com/forum/index.php?topic=1177.0

 

Another more technical thread:  http://lime-technology.com/forum/index.php?topic=1790.0.

 

Also see http://lime-technology.com/wiki/index.php?title=Improving_unRAID_Performance#Increase_Read-Ahead_Buffer.

 

Thanks again.  The machine was set for automatic updates, but had not installed SP1.  Got that installed, and now I'm seeing 25-30MB/s read performance without any "drops" to zero on a 12GB file transfer. Sweet!  Now that I know I'm getting good throughput, I'll go find out if that fixes my streaming and HDHR problems.