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Oracle® ZFS Storage Appliance Analytics Guide, Release OS8.7.x

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Updated: August 2017

When to Add More Write Log Devices (CLI)

Use the following procedure to determine if you need more write log devices for the appliance.

  1. Create a worksheet as described in Creating a Worksheet (CLI), select that worksheet, and then enter dataset.
    hostname:analytics worksheets> select worksheet-000
    hostname:analytics worksheet-000> dataset
  2. Enter set name="io.disks[utilization=90]", and then enter commit to add disks with utilization of at least 90% to your worksheet.
    hostname:analytics worksheet-000 dataset (uncommitted)> set name="io.disks[utilization=90]"
                               name = io.disks[utilization=90]
    hostname:analytics worksheet-000 dataset (uncommitted)> commit
  3. Enter done, and then enter done again to exit the context.
    hostname:analytics worksheet-000> done
    hostname:analytics worksheets> done
  4. Wait at least 10 minutes, and then go to analytics datasets.

    Note -  Ten minutes is a general guideline. This amount of time may be adjusted if you have a performance-sensitive, short-duration synchronous write workload.
    hostname:> analytics datasets
  5. Enter show to view a list of available datasets.
    hostname:analytics datasets> show
    dataset-000 active    1.27M   15.5M  arc.accesses[hit/miss]
    dataset-001 active     517K   9.21M  arc.accesses[hit/miss=metadata hits][L2ARC eligibility]
    dataset-019 active     290K   7.80M  io.disks[utilization=90]
    hostname:analytics datasets>
  6. Enter select and the dataset with the name io.disks[utilization=90].

    In this example, dataset name io.disks[utilization=90] corresponds to dataset-019.

    hostname:analytics datasets> select dataset-019
  7. Enter read 600 to read the last 600 seconds, or 10 minutes, of the dataset.
    hostname:analytics dataset-019> read 600
  8. Examine the data.

    You may want to add more write log devices when existing devices are 90% utilized.