File transfer speed consistently slows down

[mmedeiro]

Hi all,

Ill make this quick; when transfering large files I initially get speeds of 160 to 180 mbs for 25 % of the file then the speeds slow down to 30mbs. At this point I pause and then continue the xfer, the speed goes back to 180 mbps, then after 50% another drop. Any ideas?

 

[HugoStiglitz]

this is typical of spindle drives, their burst speeds are quite high but sustained transfer tends to drop off.

" The sustained data transfer rate or sustained throughput of a drive will be the slower of the sustained internal and sustained external rates. The sustained rate is less than or equal to the maximum or burst rate because it does not have the benefit of any cache or buffer memory in the drive. The internal rate is further determined by the media rate, sector overhead time, head switch time, and cylinder switch time. These are not applicable to SSDs"

http://en.wikipedia.org/wiki/Hard_disk_drive_performance_characteristics

what are the source and destination drives and what hard drive controller are you using? as 30MB/s is quite slow even for sustained transfer