WiFi vs. Ethernet access speeds on Drobo FS

i seem to be noticing SIGNIFICANTLY slower read and write access speeds to the Drobo FS when my macbook pro (MBP) (i7 Core) is connected to the network via wifi (802.11n) compared to ethernet ([color=#FF0000]100mbps[/color]… not 1000mbps). based on the sheer bandwidth of 802.11n, i would think it would be the faster of the two connections (and i have confirmed via “network utilities” the connection type is 802.11n).

here are the things i am seeing:
MBP connected via WiFi (802.11n) only

  • when copying any data type from my MBP to the Drobo FS it is much slower than any file transfer should be
  • when playing a video file from the Drobo FS on my MBP via VLC player, the file (depending on size) takes 10’s seconds to load.
  • after a video is finally loaded into VLC, the video will only play for a few seconds before it stops, “thinks,” plays another few seconds. it acts like what happens when watching a video online and the buffer runs out.

MBP connected via ethernet (100mbps) only

  • no issues that were seen when connected via 802.11n are experienced

i read a few posts about the new i7 Core not supporting jumbo frames but i doubt that this is the issue here.

does anyone have any ideas on what might be going on?

Wireless in general provides inconsistent bandwidth. And especially with streaming playback, you want consistency. Bursts are great for file transfers, but real-time playback needs a constant flow of data.

Imagine you’re drinking from a water hose, a steady flow coming in. You can easily hold the incoming liquid in your mouth while you swallow. No problem. This is a nice, steady stream. The instantaneous speed is equal to the average speed.

Now imagine your friend is controlling the faucet and changing the flow. When they turn it up to full flow you may not be able to hold the incoming water and it’ll come out of your mouth or you may choke. But when the flow is reduced you may not get any water at all. The instantaneous speed varies here, even though the average speed might be the same as the previous situation.

Streaming playback requires a certain sustained instantaneous speed (equal to whatever the bitrate of the audio+video is).
File copies don’t have such a requirement, but different operating systems measure the speed and estimated time remaining differently. The only true way to measure file copies is to time the operation yourself.

The question is, you say you have a WirelessN card, but are you actually connectined @ N speeds and maintaining them?

Are you going @ 130 or 300? Is it staying @ 130?

If it says 130 you are most likely getting more like 50-60 without interference. Like bhiga said wireless is a bit sketchy, also certain security types like WPA2 + TKIP/AES on can cause major performence issues.

What type of router are using?

Also, if you have devices connecting at N and others using A/B it can lead to performance issues. If you can do it, enable N-only mode if your router allows it. If you or neighbors also have wireless routers nearby, they can lead to interference and slower performance especially if they are using the same or nearby channels. If you see this, try adjusting your wireless channel from the default…this made a huge difference for me.

Depending on your wireless router, you can consider flashing it with DD-WRT which gives you total control over your wireless and in my experience is much more consistent in performance than most of the default firmware on routers.

I get 12 MegaBytes/second sustained transfer over Wifi-n on my 2 or 3 generation old Core 2 Duo Unibody MacBook Pro. iStat Menu says that I peaked at 16 MegaBytes/second. I can’t find any good quality ethernet cables and only get 100 megabits when plugged in, so I’m happy with my 128 megabits until I find my crimp tool and can make a new one.