Re: File transfer speed slows 10x and more after reaching 1TB in size

In my case the CPU usage was normal throughout the whole process. Are 
you experiencing high CPU usage when the problem surfaces?

In my case, I noticed that my disk was "thrashing" about while in the 
slow state, the noise made by the drive in an open case was very 
noticeable. When it was transferring normally, the disk was nearly 
inaudible. Also the approximate 1TB threshold seemed to be a sharp 
dropping point, performance quickly degraded once that point was reached.

I find it interesting that you have experienced a much smaller file size 
limit. I did create a 500GB image file made at the around the same time 
using the exact same process on the same hardware, and it behaved 
normally. As part of my tests to pin down the source of the problem, I 
copied the 500Gb image to the secondary 4TB disk and it transfered as 
expected with no noticeable performance issue.

I will need to use something for these large images, the problem makes 
JFS unusable and the thrashing may even destroy my HD. My next test is 
to switch to ext4 or XFS and do a transfer of the same 2TB image file.

On 16-02-09 01:01 AM, Jernej Simončič wrote:
> On Tuesday, February 9, 2016, 1:43:51, alanb wrote:
>
>> Using gddrescue I created a 2TB disk image file from a good 2TB drive
>> onto a good 4TB drive, the performance at the start was as expected,
>> however once it reached about 1TB the performance dropped from about
>> 100-120Mb/s down to 3-5Mb/s.
> I just noticed the exact same problem myself, except that for me
> transfer speeds drop when the file reaches around 128GB in size (which
> makes my jfs volumes unusable for storing local backup images).
>
> I did find this (I was looking at why jfscommit has high CPU usage):
> <http://sourceforge.net/p/jfs/mailman/message/27476050/>, but it
> appears that nothing has been done to address this.
>


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