Suppose I create a 16G zvol on a pool that is a disklabel partition on an SSD. I would expect read/write performance that is near the native SSD read/write speed. I got >400 MB/s on read, and only about 80 MB/s write. I wrote again, guessing that the read was returning synthetic zeros and that the first write forced allocation, but got about the same: $ time dd if=/dev/zero of=/dev/zvol/rdsk/tank0/xen-netbsd-9-amd64 bs=32m 17179869184 bytes transferred in 212.227 secs (80950440 bytes/sec) reading back: $ dd if=/dev/zvol/rdsk/tank0/xen-netbsd-9-amd64 of=/dev/null bs=32m 17179869184 bytes transferred in 81.584 secs (210578902 bytes/sec) and reading the raw disk: $ time dd if=/dev/rwd0d of=/dev/null bs=32m count=512 17179869184 bytes transferred in 62.190 secs (276248097 bytes/sec) So zvol is a fair bit slower. It's not convenient to write the raw disk any more; it's an older SSD on an older machine and maybe my expectations of >80 is confused. Do people think zvol performance is close to native? I tried to swapctl -a the zvol, which failed. I have updated the zvol section in the HOWTO: https://wiki.netbsd.org/zfs/
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