[zfs-discuss] sending stream too slow on busy system

[David Bruzos]

Hello all:
I have a reasonably busy system that I need to stream about a TB of data from in order to migrate some virtual machines to a remote site, but the zfs send is really slow.  A similar machine with no VMs running seems to send about 10-15 times faster than the busy box.
My plan is to do an initial send and then a final incremental send, in order to cut the down time to a minimum, but at this rate, it will take me a week to complete the initial send.  Of course, something is likely to go wrong during this long time, so I'll have to start over.

What are some tunable parameters that can increase ZFS streaming performance that I can play with while the system is up and running and are not likely to cause some kind a nasty crash and/or sideaffect?

Thanks!

David