2

Just recently, my system is really struggling to move large amounts of data (sometimes few big files, sometimes many small ones). The trouble occurs when the files are being moved off of my hardrive to an external system, either a mounted network share or an external USB. The network share and USB experienced the same symptoms, but I'm not sure if they are necessarily related.

The most recent example was moments ago when I tried moving a folder totalling 1.9GB from my hard drive to a USB stick, via Nautilus copy & paste. By the time the progress bar had opened, the operation was about 1/3 done, reporting 600MB transferred. The transfer rate at this time was 29MB/s, and was rapidly declining. It went from 29 MB/s to 20 MB/s in a few seconds, went from 20 to 10 in about 10 seconds, and eventually bottomed out at 6MBs. There was also a period of about 30 seconds where the whole operation seemed stalled, as in, no updates shown in the progress window. An operation like this should take only a few seconds, and ended up taking about 3 minutes.

Yesterday I tried moving this same folder onto the network share and experienced similar symptoms. It took about 30 seconds for the progress bar to reach half way, and then the whole thing just stopped. Network monitor showed a flatline 0 Bytes/s.

I have a newish SSD in the machine, so I don't think that's the bottleneck.

What kind of things should I check to track down the root of this issue?

Using Ubuntu 12.10. The files I was trying to move were in my home folder which uses encryptfs.

parker.sikand
  • 373
  • 1
  • 2
  • 9
  • 1
    Same problem for me, when the transfer starts it's fast. Then it slows down and will not finish. Stops around 5-6 MB/s but nothing happens. Works OK on FTP transfer on my network but not from HDD to USB stick. – aXept May 15 '13 at 21:01
  • More like hardware, must have large RAM and also Swap area. Also must make sure other USB peripheral are not used. It happened to me and this is my work around and it works like a charm. I transfer 200GB of files no prob after fix the prob. Hope it help you too. – Shaharil Ahmad May 16 '13 at 03:37

1 Answers1

1

"What kind of things should I check to track down the root of this issue?"

You need to look at the stuff that's common to both transfers. Were you transferring the same file? Could that file be croupt? Were you out of ram for file caching? How was your CPU?

Encrypting an partition usually has this type of side effect. Remember in order to transfer your file you have to decode it locally then transfer it to the destination. This is transparent to the copy program/calls but it still has to be done. If you are trying to transfer huge files, the memory that holds temporary decrypted copies of the file (well bit of the file) may have been full.

Check your free memory during a transfer using free -m or just free and see what it says is available for buffers and cache.

Also keep in mind that Linux caches file operations. So just because the user process thinks data has been copied doesn't mean anything has actually be written to physcal media. This causes smaller files to write really "quickly" but larger files have a "burst" of speed, then when the cache fills they slow down. It's not usually so noticeable, but if your caches are full, or your low on free memory (for new caches) or your CPU is under-powered (very common when people encrypt things), then it's going to take longer.

coteyr
  • 18,288