Why do file transfers over USB slow down my whole computer?

Question

Whenever I transfer large files, or large amounts of files, over USB to or from an external drive, the whole computer slows down to a crawl during the transfer. I'm using Ubuntu 14.04, but I've had this problem before in earlier versions. Why does this happen? I want to be able to file a bug report to stop this from happening.

Cheers,
Reid

Solution

This sounds like a classic case of system load to me.

When you read/write something to/from a drive, it needs to lookup file information. However, that file may be fragmented, in different locations, or even organized.

When you copy something from your drive to a USB, you have to read a (potentially) fragmented file and then re-write it to another storage medium. With some systems (read EXT), it is often faster than other systems (^{cough NTFS cough}). Also, if you have a bad processor, it wastes cycles for other things trying to copy things over.

There is really nothing you can do to solve this issue. There are workarounds, however:

1. Defragment your hard drive.
2. Use an EXT formatted flash drive where possible.
3. Install more memory as a "cache" space.
   1. Use excess memory as a ramdisc.
4. Use a better USB protocol.
5. Upgrade your processor/PC.
6. Get an SSD.

Comments

[Jakke]

which file systems are you using? do you have this problem with ANY usb device? Do you see any messages in dmesg or syslog? What does your process manager show (cpu usage?) when you're transferring files? Do any of your disk show any signs of errors (fsck, smartmon)? Is it only copying files or also when you open files from usb? Whether you want a proper answer here or file a bug report, you will need to hand us as much information as you can gather...

[user155708]

It's a USB 3 external hard drive using NTFS that I'm copying files to. It doesn't happen with my flash drives (all of which are USB 2), or when I'm copying small amounts of data across to the hard drive. But when I'm moving 10s of gigabytes at a time, it works fantastically, except it slows everything else down. Firefox crashes, thing's don't open. The computer basically becomes unusable.

[Jakke]

If your firefox crashes, you can enter about:crashes in the location bar and you'll see what causes the crash. At least give us some information that can give us a clue... "it makes my system unusable" is inadequate info. What's your memory like? CPU usage? System logs? IO information, does hdparm -tT /dev/<your-usb-drive> perform as expected? ... Without any information, you're not going to get any help. Also have a look at this if you're clueless: askubuntu.com/questions/293426/…

[Kai]

I think this might have to do with high disk I/O. I guess that you won't notice any problems when copying large files to any USB 2.0 device, because they are a lot slower. You could try to give the process that copies the files a lower priority using ionice; I have to admit that I have never tried that, it's only a guess that this could help.

[Glutanimate]

Ubuntu uses a userland (read: inefficient) driver for NTFS, which might be another contributing factor. However, performance dips due to high disk I/O are a general issue on Linux. There are several kernel bug reports on this, e.g. this one with over 600 comments.

[user155708]

Firefox doesn't straight crash, it just goes black and then returns again.

[Mahendran Sakkarai]

unix.stackexchange.com/a/107722/94334 which gives a fixes to the problem.

[Madhusudhan]

@Whaaaat What about DMA(UDMA). HDD copy doesn't use cpu according to DMA feature.

[PeterM]

This is not a CPU problem