1. Managing ZFS File Systems in Oracle Solaris 11.4
  2. Recommended Oracle Solaris ZFS Practices
  3. Recommended Storage Pool Practices
  4. ZFS Storage Pool Creation Practices
  5. Pool Creation Practices on Local or Network Attached Storage Arrays

Pool Creation Practices on Local or Network Attached Storage Arrays

Consider the following storage pool practices when creating an a ZFS storage pool on a storage array that is connected locally or remotely.

  • If you create an pool on SAN devices and the network connection is slow, the pool's devices might be UNAVAIL for a period of time. You need to assess whether the network connection is appropriate for providing your data in a continuous fashion. Also, consider that if you are using SAN devices for your root pool, they might not be available as soon as the system is booted and the root pool's devices might also be UNAVAIL.

  • Confirm with your array vendor that the disk array is not flushing its cache after a flush write cache request is issued by ZFS.

  • Use whole disks, not disk slices, as storage pool devices so that Oracle Solaris ZFS activates the local small disk caches, which get flushed at appropriate times.

  • For best performance, create one LUN for each physical disk in the array. Using only one large LUN can cause ZFS to queue up too few read I/O operations to actually drive the storage to optimal performance. Conversely, using many small LUNs could have the effect of swamping the storage with a large number of pending read I/O operations.

  • A storage array that uses dynamic (or thin) provisioning software to implement virtual space allocation is not recommended for Oracle Solaris ZFS. When Oracle Solaris ZFS writes the modified data to free space, it writes to the entire LUN. The Oracle Solaris ZFS write process allocates all the virtual space from the storage array's point of view, which negates the benefit of dynamic provisioning.

    Consider that dynamic provisioning software might be unnecessary when using ZFS:

    • You can expand a LUN in an existing ZFS storage pool and it will use the new space.

    • Similar behavior works when a smaller LUN is replaced with a larger LUN.

    • If you assess the storage needs for your pool and create the pool with smaller LUNs that equal the required storage needs, then you can always expand the LUNs to a larger size if you need more space.

  • Present individual devices in JBOD-mode and configure ZFS storage redundancy (mirror or RAID-Z) on this type of array so that ZFS can report and correct data inconsistencies.