Copy BSD Partition to other disk

Source pastition: /dev/ad0s1a
Destination partition: /dev/ad1s1a

dd if=/dev/ad0s1a conv=notrunc,noerror,sync bs=64k | dd of=/dev/ad1s1a bs=64k
fsck /dev/ad1s1a

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Backup disk over SSH:

Backup
dd if=/dev/ada0 | gzip -1 - | ssh user@hostname dd of=image.gz

Restore
ssh user@hostname dd if=image.gz | gunzip -1 - | dd of=/dev/ada0