Question Copying entire drives. Slow downs

[Music Lover123]

Hi

Windows 10 up to date.
i7 8700k
Prime Z370 A Mobo
32gb ram


I am replacing smaller SATA data drives with larger SATA data drives. I am using Retrospect 7.6 to copy the entire drive contents from the old drives to the new ones. The drives are mounted into the internal SATA ports. I finished copying one drive to another and the speed was very good. 2900 MB/minute. This was a 5400 rpm 4tb drive to a 7200 rpm 8tb drive.
Now I am copying a 5400 rpm 2tb to a 5400 rpm 4tb drive and speed is about 500 MB/minute. All drives are mounted on internal SATA ports.

Why the difference in speed? This latest copying operation is copying a lot of large files, so it should be close in speed when accounting for the slower RPM, but it's much slower, one-sixth the speed !?

... Hey, chime in if there's a better way to copy drives.

Thank You for any comments.

 

[Grobe]

Most likely you use HDD that use Shingled magnetic recording (SMR). This is the most probable reason.

 

[hotaru.hino]

The initial burst in speed is likely due to the transfer hitting cache or some other "faster" memory. Most file operations tend to be tiny, so rather than have the application wait for the data to be written, the storage controller shoves it in cache and says "yeah, the operation's done" and actually commits the write operation later. If you exceed this cache limit and are still transferring things, the performance will drop to what the actual performance is.

Also no hard drive is capable of 2900 MB/sec of actual performance. This right there should've been seen as suspicious.

 

[Music Lover123]

The initial burst in speed is likely due to the transfer hitting cache or some other "faster" memory. Most file operations tend to be tiny, so rather than have the application wait for the data to be written, the storage controller shoves it in cache and says "yeah, the operation's done" and actually commits the write operation later. If you exceed this cache limit and are still transferring things, the performance will drop to what the actual performance is.

Also no hard drive is capable of 2900 MB/sec of actual performance. This right there should've been seen as suspicious.

2900mb/minute not second. I wonder if restarting between copying drives would speed things up.

...now I'm copying the second drive. The speed at the moment is about 1200mg/minute. Actually it's fluctuating between 1000 and 1800 mg / minute

Is copying slower for very large files or many very small files. and faster for medium size files? Don't know why the speed fluctuates so much?

thanks for the comments