How can I best back up a ZFS volume to a USB hard drive?

(I feel like I've violated plenty of common-sense stuff while learning ZFS. If so, you can let me have it in the comments.)

I have a large RAID-Z1 array that I back up to a USB 3.0 hard drive. I'd also like to maintain zfs-auto-snapshot's snapshots as well. I've been doing a zfs send MyArray | zfs recv Backup and it's been working pretty well; however, once in a while, the array will become suspended due to an I/O error, and I'll either need to reboot, or rarely, destroy the backup disk and re-copy everything.

This seems like I'm doing something wrong, so I'd like to know: what is the best way to back up a ZFS array to a single portable disk?

I would prefer a portable backup solution like backing up to a single USB hard drive (preferably so I can buy two and keep one somewhere secure), but I'm open to getting a small NAS and zfs sending over a network.