Balance to multiple drives when receiving multiple incoming file transfers

I'm in the midst of transferring a large volume of data from an 8-bay NAS into a new DrivePool setup and I'm trying to speed up the process a bit. I tried using the SSD plugin with a 500 GB SSD to enable greater bandwidth for multiple file copy operation simultaneously, but the balancer can't keep up with the workload and the SSD fills up faster than it can evacuate. The issue seems to be that while the balancer is evacuating files from the SSD, it only places them on one drive at a time, despite the fact that several of the drives in the pool are below the "full" threshold. Many of the drives in my pool are slow Seagate Archive drives that have poor write speeds, so if the balancer limits itself to writing to only one drive at a time, it'll never be able to keep up with large volumes of incoming data.

 

How can I configure DrivePool to balance incoming transfers across multiple drives in the pool simultaneously so that it can better handle large volumes of incoming data, either with OR without an SSD landing zone? The Archive drives are able to sustain reads at the normal 100+ MB/s, but writes are extremely variable, dropping into the single digits at times. Therefore, my pool is presently unable to accomodate the full speed of even ONE single incoming transfer. If it could be configured to balance incoming transfers across multiple drives simultaneously, it would really speed up the process.

 

I've also been evaluating Drive Bender, and while I prefer DrivePool's interface, Drive Bender appears able to send multiple incoming transfers to separate drives in the pool without issue, and without any special configuration required.