My Speed drops in middle of the transfer i got 10GB switch  if i copy 1gb file it get speed of 420-490 MB/sec but when i copy large file my speed drops to 90MB/sec in the middle of the transfer any1 had this issue ? on my other unraid server which is install on bare metal i get consistence speed during the transfer. need any help please 

First few GBs of any transfer are cached to RAM, IIRC 20% free RAM by default, so initial speed is much faster, up to line speed, after that you are limited by the actual device writing speed.

@johnnie.black thanks for the reply will it help if i allocate more ram to the VM. and on my other unraid server which i install on bare metal i get the same speed start to finish it fluctuate 30-40MB not much. 

For mostly smaller transfers you can get good results by increasing RAM (or RAM cache) size, for larger transfers only by using faster devices that can keep up, like NVMe devices or a multi device raid0/5/10 cache pool.

 

 

@johnnie.black thanks for your help much appreciated i increase the ram to 64GB and my transfer speed increase to 500-600 MB  and its consistence through out the transfer even for larger files.