Why so slow?

Hi All,

So here’s my scenario:

iMac wifi to my Airport Extreme.
USB 2.0 HD connected directly to the USB port on my Airport Extreme.
Drobo FS Ethernet connected directly to a port on my Airport Extreme.

When I copy a file from my Drobo FS to my USB HD, it’s so slow - I’m guessing that the file needs to go wifi through my iMac, as the two drives are SMBs. Is there a way to do that kind of file copy FASTER?

I’d guess that since I’m using 802.11n, that the wifi wouldn’t cause it to go so slowly… 54Mbps, right?

A 9GB file takes about an hour to copy. Something seems wrong.

  • Thanx
  • Jon

The file is going through your MAC, via wireless, twice:

Drobo FS—>Mac---->USB HD

You are getting 2.5MB/s (bytes, big B, not bits, little b). 54mb/s = 5.4MB/s (best case, but generally less)

That sounds about right. 802.11n can go faster. Theoretically 150 or 300mb/s but good luck getting anywhere near that unless you are close enough that you ought to just run a 10 foot ethernet cable. In the real world most people get about 5-9MB/s (at best) even if they stand on their head and pray to the deity of their choice :slight_smile:

I’m not very familiar with the FS so there may be a smarter way to do this, circumventing the MAC…

Try a wired connection for the first problem resolution step.

Hey NeilR,

Thanks for the note. Yeah, hm. So I wonder if there’s any way to get the file transferred without going through my Mac. Seems like there’s gotta be a smarter way to transfer the file… If I initiated it on the Drobo, then I wouldn’t need to go through my Mac. Can I do it via telnet?

  • Jon

small correction, everything else is good

54 Mb/s = 6.75 MB/s
divide by 8 not 10.

unless you can get a command line going on the extreme, which i don’t think you can, but don’t have one, so not sure, there’s no way to copy from drive to drive on it.

Technically you may be able to mount the USB-shared drive from the Airport Express on the DroboFS directly, but by the time you get DroboApps, SSH, mounting parameters, etc sorted out, you might as well just connect the Mac to gigabit ethernet (via long cord or whatever) and just copy it the slow way.

Speaking as someone who just copied 1.5TB from a DroboFS to a Time Capsule, I can empathize.

waw74, For real world throughput (the amount of DATA that actually gets moved) I think it is somewhat conventional or at least common practice to divide by 10 instead of 8 to account for the mandatory parity checking. One or two bits always accompany each 8 bits down the line. In real life there is much more overhead but this is the minimum, especially over Ethernet and more so wireless because that adds yet more overhead.

Edit: and yes, I should have said something to that effect when I quoted the number :-).