Stalls at high speed. Restarts from low speed.

[johnav1989]

Hello,

I am running a 300GB sync Job from a SAN to a USB 3.0 hard drive. The problem I encounter is that when I start the job the transfer speed shoots up to ~200Mbps and then the sync stalls. After a few moments the sync resumes at ~20Mbps and gradually climbs back to ~200Mbps and the cycle continues over and over. My current work around has been to change the setting "RunWithBackgroundPriority Enabled" to "true" within the "Global Settings" xml document; however this cuts the transfer speed in half.

While this enables me to load hard drives at the moment I would really like to get the highest speeds possible as I load entire hard drives on a daily basis.

Thanks in advance for your help!

-John

[Zenju]

This is normal behavior of buffered usb devices: While the usb file buffers are filled (= no physical write operation) transfer times seemingly skyrocket, only to later plummet when the buffers are flushed (= physical write operations) and the application stalls while waiting for the usb write to finish. This is not caused by FFS, but by the implementation of the usb drivers. The fastest transfer times are seen with the FFS default settings.

[johnav1989]

This is normal behavior of buffered usb devices: While the usb file buffers are filled (= no physical write operation) transfer times seemingly skyrocket, only to later plummet when the buffers are flushed (= physical write operations) and the application stalls while waiting for the usb write to finish. This is not caused by FFS, but by the implementation of the usb drivers. The fastest transfer times are seen with the FFS default settings.

Ok. This makes sense to me. However, FFS seems to hang every minute or so as a result. This makes something as simple as minimizing and maximizing the software difficult. Is this standard behavior?

[Zenju]

Hm, it's standard behavior for most usb drives which do a bulk of work without calling back the application. This non-responsiveness issue could be solved from two ends: 1. the usb driver should call back after shorter intervals of time (like 100 ms instead of 10 seconds) just like most other data storages do. Or FFS could run the copy process asynchronously, thereby increasing the internal program complexity for "only" a cosmetical problem. In both cases performance characteristics would be the same (i.e. the same strange faster/slower perf curve), but FFS's window would be responsive and allow simple tasks like minimizing, moving.