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NFS + Wi-Fi Bandwidth Concerns because of TV Recording
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Author:  crasarx [ Sat Apr 08, 2006 9:45 pm ]
Post subject:  NFS + Wi-Fi Bandwidth Concerns because of TV Recording
Hello,

I recentely set up a box running KnoppMyth to record TV programs. I'm recording programs to a central server, but do not want to have an ethernet cable running across my living room. I'd like to use Wi-Fi bridge instead (I have an 802.11g WAP). My concern, however, is that the latency and limited bandwidth of the wireless might not be able to keep up with the output of the MythTV box. Is this going to be a problem or can NFS locally cache things and send them at a slower pace to ensure everything gets to the central server?

Thanks in advance!
Author:  tjc [ Sun Apr 09, 2006 8:39 am ]
Post subject:  Re: NFS + Wi-Fi Bandwidth Concerns because of TV Recording
crasarx wrote:
My concern, however, is that the latency and limited bandwidth of the wireless might not be able to keep up with the output of the MythTV box. Is this going to be a problem or can NFS locally cache things and send them at a slower pace to ensure everything gets to the central server?

A valid concern. I've done the math for folks on a couple of occasions. The answer is, "it depends". Caching exists and can help some, but given the sheer volume of data we're talking about... It all depends on how noisy your RF environment is, and how many network stalls you experience as a result. Watching "live tv" with the storage on an NFS mounted partition over wifi could definitely be an iffy proposition.

Remember DMA is generally considered to be essential for a local HD to keep up with the data. Given DMA a HD has plenty of bandwidth by a factor of 10 or 20 for SDTV, but without it problems crop up very quickly just due to latency.
Author:  sanger440 [ Mon Apr 10, 2006 5:15 pm ]
Post subject: 
Greetings,

I have set up a Slavebackend in my bedroom and use a a wireless nic to connect to the masterbackend down stairs. I followed the instructions on LINHES to set it up.

I mostly just watch recordings from the mbe on the sbe upstairs and it usually works very well. Sometimes if the mbe is recording and I am upstairs watching another recording the sbe will be a little choppy. I also use the tuner on the sbe to record to the mbe when I have two shows on the same time. (my mbe does not have another pci slot to install two tuners). The BTTV card on the sbe usually records nicely over the wireless connection. But sometime there may be a little chop here and there.


I am using a D-link 108g router downstairs and on the sbe I use a generic 54g wireless nic made by airlink (uses the mad-wifi drivers). When I first set up the sbe/mbe, I had a wireless nic on the MBE also and it worked well. Since then I have run some cat 5 to the mbe.

I never thought the wireless set up would be able to stream recordings but since an airlink NIC is like 10 bux, I thought I would try it. I was pleasantly surprised to say the least.

Hope this helps
Author:  yamez [ Thu Apr 13, 2006 5:40 am ]
Post subject: 
Depends on overhead too. Ethernet cable never gets 100 Mb/s, same with Wi-Fi, but worse. Check this link to see what real speeds you will get which is generally correct from my experience.

http://www.deviceforge.com/articles/AT5096801417.html

Wireless LAN Throughput by IEEE Standard
IEEE WLAN Standard Over-the-Air (OTA) Estimates Media Access Control Layer, Service Access Point (MAC SAP) Estimates
802.11b 11 Mbps 5 Mbps
802.11g 54 Mbps 25 Mbps (when .11b is not present)
802.11a 54 Mbps 25 Mbps
802.11n 200+ Mbps 100 Mbps
Author:  crasarx [ Mon Apr 17, 2006 2:20 pm ]
Post subject: 
I just set up a bridge using 802.11g, and so far, playback alone seems to work fine. I wonder if recording + playback will chop up. I will try that soon and report back here with my results.
Author:  crasarx [ Tue Apr 18, 2006 11:41 am ]
Post subject: 
So it seems playback worked well, but recording really didn't work. I've since gone back to using CAT5 cable. Oh well.
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