I have made some more tests about the behaviour of special vdevs to become clear about use cases as technical details are still quite rare.
http://napp-it.org/doc/downloads/special-vdev.pdf 1. About Allocation Classes 2. Performance of a slow diskbased pool 3. With special vdev (metadata only) 4. With special vdev (for a single filesystem) 5. With special vdev (for a single filesystem) and Slog (Optane) 6. Performance of a fast diskbased pool 7. Fast diskbased pool with special vdev 8. NVMe Pool vs special vdev (same NVMe) 9. Compare Results 10. Conclusion 11. When is a special vdev helpful 12. When not 13. General suggestions Anything wrong about my conclusions? gea @napp-it.org -- ------------------------------------------ illumos: illumos-discuss Permalink: https://illumos.topicbox.com/groups/discuss/T7dbc47cd249baa9c-M108ee254080915b3c34b2a9d Delivery options: https://illumos.topicbox.com/groups/discuss/subscription
