Dynamic Striping in a Storage Pool

ZFS dynamically stripes data across all top-level virtual devices. The decision about where to place data is done at write time, so no fixed-width stripes are created at allocation time.

When new virtual devices are added to a pool, ZFS gradually allocates data to the new device in order to maintain performance and disk space allocation policies. Each virtual device can also be a mirror or a RAID-Z device that contains other disk devices or files. This configuration gives you flexibility in controlling the fault characteristics of your pool. For example, you could create the following configurations out of four disks:

• Four disks using dynamic striping

• One four-way RAID-Z configuration

• Two two-way mirrors using dynamic striping

To ensure efficient use of ZFS, use top-level virtual devices of the same type with the same redundancy level in each device. Do not combine different types of virtual devices within the same pool, such as using a two-way mirror and a three-way RAID-Z configuration.