Testing a cache tier

Since our cache tier is ready, during the write operation, clients will see what is being written to their regular pools, but actually, it's being written on cache-pools first and then based on the cache tier policy data, it will be flushed to the storage tier. This data migration is transparent to the client.

How to do it…

  1. In the previous recipe, we created a 500 MB test file named /tmp/file1; we will now put this file in an EC-pool:
    # rados -p EC-pool put object1 /tmp/file1
  2. Since an EC-pool is tiered with a cache-pool named file1 should not get written to the EC-pool in the first step, however, it will get written to the cache-pool. To verify this, list each pool to get the object names. Use the date command to track the time and changes:
    # rados -p EC-pool ls
# rados -p cache-pool ls
# date
    How to do it…
  3. After 300 seconds (as we have configured cache_min_evict_age to 300 seconds), the cache-tiering agent will migrate object1 from the cache-pool to the EC-pool, and object1 will be removed from the cache-pool:
    # rados -p EC-pool ls
# rados -p cache-pool ls
# date
    How to do it…

    If you take a closer look at Step 2 and 3, you will notice that data has migrated from the cache-pool to the EC-pool after a certain amount of time, which is totally transparent to the users.

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