[justincormack]

Use rsync. It now preserves the buffer cache status that files had before so it does not stomp on your allocations.

http://insights.oetiker.ch/linux/fadvise/

[mceachen]

Also, consider using --bwlimit to throttle the copy speed, so the spindle can still respond to other IO requests. (25-50% of unthrottled speed seemed to be a reasonable tradeoff).