PowerScale OneFS 9.8.0.0 Web Administration Guide

SSD strategies

OneFS clusters can contain nodes that include solid-state drives (SSD). OneFS autoprovisions nodes with SSDs into one or more node pools. The SSD strategy defined in the default file pool policy determines how SSDs are used within the cluster, and can be set to increase performance across a wide range of workflows. SSD strategies apply only to SSD storage.

You can configure file pool policies to apply specific SSD strategies as needed. When you select SSD options during the creation of a file pool policy, you can identify the files in the OneFS cluster that require faster or slower performance. When the SmartPools job runs, OneFS uses file pool policies to move this data to the appropriate storage pool and drive type.

The following SSD strategy options that you can set in a file pool policy are listed in order of slowest to fastest choices:

Avoid SSDs

Writes all associated file data and metadata to HDDs only.

CAUTION:Use this option to free SSD space only after consulting with Dell Technologies Support. Using this strategy can negatively affect performance.

Metadata read acceleration

Writes both file data and metadata to HDDs. This is the default setting. An extra mirror of the file metadata is written to SSDs, if available. The extra SSD mirror is included in the number of mirrors, if any, required to satisfy the requested protection.

Metadata read/write acceleration

Writes file data to HDDs and metadata to SSDs, when available. This strategy accelerates metadata writes in addition to reads but requires about four to five times more SSD storage than the Metadata read acceleration setting. Enabling GNA does not affect read/write acceleration.

Data on SSDs

Uses SSD node pools for both data and metadata, regardless of whether global namespace acceleration is enabled. This SSD strategy does not result in the creation of additional mirrors beyond the normal requested protection but requires significantly increased storage requirements compared with the other SSD strategy options.

Note the following considerations for setting and applying SSD strategies.

• To use an SSD strategy that stores metadata and/or data on SSDs, you must have SSD storage in the node pool or tier, otherwise the strategy is ignored.
• If you specify an SSD strategy but there is no storage of the type that you specified, the strategy is ignored.
• If you specify an SSD strategy that stores metadata and/or data on SSDs but the SSD storage is full, OneFS attempts to spill data to HDD. If HDD storage is full, OneFS raises an out of space error.