mirror vdev
also: RAID-1 vdev, mirrored vdev
A mirror vdev is a RAID-1 storage pool device in ZFS where data is simultaneously written to two or more physical devices, providing redundancy and fault tolerance.
In ZFS (Zettabyte File System), a mirror vdev duplicates all data across multiple physical drives or block devices. If one device fails, the pool continues operating normally using the remaining copies of the data.
A basic mirror vdev typically consists of two devices, though you can create mirrors with three or more devices. When you write data to a mirror vdev, ZFS writes identical copies to each member device. Read operations can be load-balanced across the devices, improving performance.
Example: Creating a ZFS pool with mirror vdevs:
zpool create mypool mirror /dev/sda /dev/sdb mirror /dev/sdc /dev/sddsda and sdb, another mirroring sdc and sdd. If sda fails, data is still accessible from sdb.Mirror vdevs differ from RAID-Z vdevs, which use parity instead of full duplication and provide better storage efficiency at the cost of more complex recovery.