Strategies and questions about NAS to NAS data transfers

Certainly people will see more and more of the painstakingly slow performance of budget NAS devices as they are beginning to proliferate the business and home markets.

We are copying ~2TB from a Western Digital NAS to a QNAP with RSync. Because it looks like SSH is causing high CPU usage on the WD, we are considering 1 of 2 options: create cron job with rsync to run after hours or attempt to speed up the copy by mounting 2 nfs shares and then run rsync. Perhaps the encryption of SSH traffic is causing the copy to be slow. I’ll try to remember to post back results but please pipe up if you’ve had better success copying NAS to NAS with nfs and rsync or a different method entirely. 

I’m also currently running FastCopy v2.1 to copy around 640GB to a single usb-attached sata drive. RichCopy error-ed out a couple times after a few hours. After 70GB I switched to fast copy and fast forward 8 hours, 190GB of data had copied which seems like a big improvement in performance.

What’s the ideal way to get the best performance out of these types of devices regardless of volume size and RAID type?