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SmartPools file pool policies can be used to broadly control the three principal attributes of a file, namely:
A file pool policy is built on a file attribute the policy can match on. A file pool policy can use any of these attributes: File Name, Path, File Type, File Size, Modified Time, Create Time, Metadata Change Time, Access Time, or User Attributes.
Once the file attribute is set to select the appropriate files, the action to be taken on those files can be added. For example, if the attribute is File Size, additional settings are available to dictate thresholds (all files bigger than x, smaller than y). Next, actions are applied. Move to node pool x, set to y protection level, and lay out for z access setting.
File attribute | Description |
File Name | Specifies file criteria based on the file name |
Path | Specifies file criteria based on where the file is stored |
File Type | Specifies file criteria based on the file-system object type |
File Size | Specifies file criteria based on the file size |
Modified Time | Specifies file criteria based on when the file was last modified |
Create Time | Specifies file criteria based on when the file was created |
Metadata Change Time | Specifies file criteria based on when the file metadata was last modified |
Access Time | Specifies file criteria based on when the file was last accessed |
User Attributes | Specifies file criteria based on custom attributes (see Custom File Attributes) |
AND and OR operators allow for the combination of criteria within a single policy for extremely data manipulation.
When a file is created in a directory with an associated path-based file pool policy, it is automatically written to the node pool specified in that policy. It does not require a SmartPools job to run. Files that match file pool policies based on attributes other than path are initially written to a default node pool. If necessary, the files are moved to the node pool specified in their matching file pool policy the next time a SmartPools job runs. This functionality ensures that write performance is not sacrificed for initial data placement.
As mentioned in Node pools, any data not covered by a file pool policy is moved to a tier that can be selected as a default for this purpose. If a disk pool has not been selected for this purpose, SmartPools defaults to the node pool with the most available capacity.
In practice, default file pool policies are almost always used because they can be so powerful. Most administrators do not want to set rules to govern all their data. They are mostly concerned about some or most of their data in terms of where it sits and how accessible it is. However, there is always data for which location in the cluster is going to be less important. For this data, there is the default policy, which is used for files for which none of the other policies in the list have applied. Typically, the default policy is set to optimize cost and to avoid using storage pools that are required for other data. For example, most default policies are at a lower protection level and use only the least expensive tier of storage.
When a file pool policy is created, SmartPools stores it in the OneFS configuration database with any other SmartPools policies. When a SmartPools job runs, it runs all the policies in order. If a file matches multiple policies, SmartPools applies only the first rule it fits.
For example, consider a scenario with the following two rules:
If the JPG rule appears first in the list, all JPG files smaller than 2 MB will go to nearline, not the performance tier. As mentioned, criteria can be combined within a single policy using AND or OR so that data can be classified granularly. To have all JPG files larger than 2 MB moved to the archive node pool, you can construct the file pool policy with an AND operator to cover that condition.
Policy order and policies themselves can be easily changed at any time. Policies can be added, deleted, edited, copied, and reordered.
Figure 12 and Figure 13 illustrate a common file pools use case. An organization wants:
As the list of file pool policies grows, it becomes less practical to manually go through all of them to see how a file will behave when policies are applied. SmartPools supports up to 128 policies. SmartPools also has some advanced options that are available on the command line for this kind of scenario testing and troubleshooting.
File pool policies can be created, copied, modified, prioritized, or removed at any time. Also provided are sample policies that can be used as is or as templates for customization.