Slow backup to external drive

I’m trying to backup “My Documents” (about 100 GB) to an external drive via a USB 2.0 port using Windows XP Home edition & the latest version of CBU. When I tested CBU on a single 100 MB file, the copy took roughly 7 seconds (about 14 MB/sec). For “My Documents”, the estimated completion time is 14 days & the copy speed is 5 MB/MINUTE. In order to reduce the required time, I’m not using any compression. What’s wrong?

It could be that you have many (thousands or tens of thousands) files and folders and this is slowing down the backup speed.


Thanks Emanuel for your prompt reply.

Indeed, “My Documents” does consist of many files & folders. The problem is that any single file of this batch is taking much longer to copy than I expected. For example, the same 100 MB file used as a single file test takes less than 10 seconds to copy compared with 20 MINUTES when included in the batch “My Documents.”

Help out there!

Surely someone must suspect what I’m doing wrong? I can’t believe that this program normally takes 15 days to back up “My Documents.” An alternative backup program took less than 45 minutes, but I like CBU better. Please note that I ran both backup programs without compression.

Sometimes the progress might display wrong information, for example it might say it takes 15 days, but if you let it run for a few hours it will drop to less.
Please enable logging to file (in backup step 4) and let the backup run for an hour, then take a screenshot and post it here with the log of the backup operation.


Thanks for your prompt reply Emanuel.

I did just as you suggested, fully expecting the same snail-like backup performance. Instead, the backup job was blazingly fast, taking only about 1 hour, not 2 weeks, & backing up at a rate of 20MB/sec, not 5 MB/min. I’m perplexed. As far as I can tell, I didn’t do anything differently from my previous efforts (except, maybe, to select Disk (Network) Usage: = High, whereas I probably had set this to Normal previously). Still, I wouldn’t have expected such a difference is backup speed. At this point, my problem appears to have been resolved, & I’ll keep an eye on this.

I have used the process explorer to monitor the reason for the slow backup. The speed of a backup can vary by more than a factor of ten from one moment to another with no explanation that I can see.

The difference between the slow and the fast backups has to do with how closely together the bursts of traffic to the disk are.

The burst usually peak at up to 10Mbytes (per secind?). But the distance between the bursts varies wildly. In the interval between bursts, I see about 600Kbytes. In beytween the bursts there is very little cpu usage and no other disk traffic. Even if I shut down every process in sight that will not kill the operating system, there is no improvement. I dicsonnect from the internet and even shut down my anti-virus. I up the priorities on the backup program and lower the priorities on other things.

On some occasions that backup will be fast and others extremely slow. For the last several days my daily backup of 107Gbytes is scheduled to take 20 hours. I kill it in the morning because I cannot afford to tie up my machine that long and I am hoping to get the problem fixed.

The USB2.0 port I am using is optimized for performance. Cache is either on or off. It makes no difference.