Determining whether tiering is appropriate for your storage environment

Before you tier data from disk storage on directory-container storage pools to cloud or tape storage, review the information about storage types and determine which type best meets your business requirements. In general, cloud and tape are appropriate for long-term storage of data that is infrequently accessed and that does not require quick retrieval.

Consider the advantages and disadvantages of each storage type:

Disk storage on directory-container storage pools

Disk storage on directory-container storage pools (subsequently referred to as disk storage) is useful for data that must be frequently accessed and quickly retrieved. However, disk storage is typically more expensive than cloud or tape storage. For this reason, some users tier their data to cloud or tape storage to achieve space savings and reduce costs. The amount of space savings depends on how well the data is deduplicated on disk. If the data is efficiently deduplicated on disk, you might not achieve the expected space savings by tiering the data.

Tip: To determine whether data is effectively deduplicated on disk, take one of the following actions:

• Generate data deduplication statistics by using the GENERATE DEDUPSTATS command. Then, view the statistics by using the QUERY DEDUPSTATS command.
• From the administrative client, run the SELECT * from SUMMARY command. For examples, see Viewing data deduplication statistics.

In general, if the data deduplication ratio is 4:1 or better, the data is efficiently deduplicated. For example, if you have 100 KB of data and reduce the size to 25 KB, the data deduplication is considered efficient. If the ratio is less than 4:1, deduplication is not efficient.

If the data on disk storage is not efficiently deduplicated, and there is no requirement to quickly retrieve the data, consider tiering the data to cloud or tape storage frequently with a brief tiering delay.

Cloud storage

Cloud storage can be more scalable and cost effective than disk storage. However, the time that is required to retrieve data from the cloud is typically longer than from disk. For cloud tiering, you must find a cloud provider that uses the Microsoft Azure cloud computing system or a cloud computing system that uses the Simple Storage Service (S3) protocol, such as IBM Cloud™ Object Storage or the Amazon Simple Storage Service (Amazon S3). For the latest information about cloud object storage services that are supported, see technote 2000915.

Tape storage

Tape storage can be more scalable and cost effective than disk storage, but the time that is required to retrieve the data from tape is typically longer than from disk. For small file workloads (with an average file size of 50 KB or smaller), the process of tiering data to tape can take more time than a typical tiering window allows for. You must also consider the effort that is required to share tape drives and coordinate access to tape volumes.

Tip: To calculate average file size, use the IBM® Db2® Command Line Processor to run the following commands:

db2 "connect to tsmdb1"
db2 "set schema tsmdb1"
db2 "select avg(logical_size) from sc_all_objects for read only with ur

Before you tier data to tape, review the following flowchart. The conditions in the flowchart might not apply to all storage environments. Additional considerations, which are not in the flowchart, might influence your decision. Make the decision that helps you meet your business requirements.

To select a tiering option, review the flowchart.

For more detailed guidelines, see Detailed guidelines about tiering by age versus tiering by state.