Neil Turner's Blog

Blogging about technology and randomness since 2002

Slow file transfers

Here’s one for you networking geeks. I’m currently sat in front of two computers – my MacBook, running OS X 10.4.9, and my parents’ desktop, running Windows XP SP2. They’re connected to each other by a 100 Mbps switch, which then connects to the main house router.

If I were to copy a file from my MacBook to the desktop using SMB, it will happen relatively quickly – several megabytes will take several seconds. The inverse, however takes much longer – copying a file from the desktop to the MacBook will take several minutes. A 45 MB file going one way will take a mere 90 seconds; the other way, it’ll take over 20 minutes.

So what’s going on? Any ideas?


  1. The XP desktop doesn’t have a modem by any chance, does it? I remember running into a case where a system had a dial-up setup for ‘net access, as well as an ethernet card for network access. The TCP/IP tweaks were set to improve the dial-up speed, but totally hosed the ethernet settings.
    Otherwise, I’m stumped, but I’d try disabling all other network/dial-up adapters in the system and possibly take the hub out of the equation by connecting the systems via a cross over ethernet cable.

  2. Are you sure it’s entirely a networking problem?
    While networking may play a part, I suspect from your description that there are two factors at play:
    First, the hard drives. Every hard drive reads considerably faster than it writes. Your laptop’s hard drive is almost certainly 5,400 RPM (or if you got the 200 GB drive upgrade, it’s 4,200 RPM). The desktop PC’s hard drive is probably 7,200 RPM.
    The write speed of the desktop’s hard drive is probably on par with the read speed of the laptop’s hard drive. But going in the other direction, the write speed of the laptop’s hard drive is significantly slower than the read speed of the desktop’s hard drive. This should account for some of the slowness.
    The second factor is FileVault. Assuming it’s turned on, any file transferred into your Mac user account’s home directory must be encrypted on-the-fly before being written to the hard drive. The network transfer will only go as fast as the files can be passed through FileVault.
    I suspect the combination of these two issues are what’s causing the slowness, not the network. You can test this by taking the network out of the equation and running three tests.
    Take the same 45 MB of files you were transferring across the network and place them on a USB thumb drive (an external hard drive would be better if you have one).
    Test 1: As a control, copy the files to the PC from the device. This will give you a maximum speed to expect on the laptop.
    Test 2: Copy the files from the device to somewhere in the home directory on your laptop.
    Test 3: Copy the files to a place outside your home directory, unprotected by FileVault.
    Test 1 should produce results roughly the same as the network transfer. Maybe a little faster or slower, depending on the speed of the device.
    Test 2 will tell you whether it’s the network or the computer to blame. If it’s about the same speed as the network transfer, then the problem exists within the laptop. If it’s noticeably faster, the problem exists somewhere in the network connection.
    Test 3 will tell you whether FileVault is causing a significant slow-down when writing files to disk.
    (Sorry this is such a long comment. I hope it’s helpful. I’ll keep up with the comments in case I can provide more advice. Also, if you want, feel free to e-mail me about this.)

  3. Jake: There is a 56k modem in the machine, but it’s never been used. But I’ll look into it.
    Greg: Well, FileVault is disabled, so that’s not it. And copying larger files from CDs is quicker – installing World of Warcraft, which is 9 CDs worth if you include the expansion and clocks in at several gigabytes, takes a little over half an hour to copy to the MacBook hard drive. That’s about the same time as it takes 45 MB to be copied from the desktop to the Mac.
    Someone on Facebook suggested it could be the virus scanner, but I can’t imagine it’d make that much difference.
    And to complicate things further, to browse to a folder on the desktop using the Mac and pulling the file over (rather than pushing it from the desktop to the Mac) works at full speed. So it’s only when a file transfer is instigated by the desktop.
    Unfortunately as of this afternoon I’ll be around 50 miles away from the desktop machine so this may have to remain a mystery for now…

  4. I also have the same issue when i copy from a ny machine such as linux/bsd/osx and so on to windows machine.
    but if i reboot to a windows on the same network its fine

  5. This is the issue bothering me for a while when copy information from one company to another, especially from different operation systems.
    So i try to copy to an ext hard-drive.

  6. I’m suffering the same thing.. I have a feeling it’s something to do with the number or size of SMB sockets at the Mac (or BSD or Linux) end…
    If I find out what it is, I’ll be sure to know.

  7. Any real solution to slow networking problem? Copying files from Windows to Mac takes hours and I am clueless.

  8. Did you ever happen to figure out how to fix this problem? I’m also unable to transfer at full speed; copying from Tiger to Windows XP occurs rapidly, while copying in the reverse direction happens at a snail’s pace. It literally takes hours — sometimes several hours — to move or copy files from my Windows drive to my Mac’s.

  9. Guess what ? it’s not just about transferring from mac to windows — transferring from mac to mac is molasses slow. What is the deal with os x network speeds? they are crappy, buggy, and that’s all there is to it even tho apple won’t acknowledge and still hasn’t fixed. all the discussion forums are replete with documented problems and bugs.
    my situation: imac g5 supposedly capable of gigabit speeds transferring to slower 100mbs capable older b/w mac so of course limited to its capability still can’t muster a sustained 400kb/s. altho the helios lan test showed it should be able to get to 7MB/s — nowhere near that. so what is up with os x and the unresolved network bugs which also affect safari, internet speeds, spinning beachballs/pinwheels etc.
    both hard drives are 7200 … btw
    great site — just found it — thanks!!!

  10. I work in a publishing company where we all use Macs. Mine is a G5 iMac, which until recently was fine. Then it began to take a LONG time to copy files from our Mac server. No other Macs had a problem. After a lot of tinkering, I changed the Network>Ethernet values to Configure: Manually, Speed: 10BaseT/UTP. 10 Base? Well, files are now copying again at a reasonable pace, but slow down drastically if I use the 100Base setting… There’s something amiss in OSX, but I don’t know what it is…