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PowerScale OneFS Web Administration Guide

Disk-usage calculations

For each quota that you configure, you can specify whether physical or logical space is included in future disk usage calculations.

You can configure quotas to include the following types of physical or logical space:

Type of physical or logical space to include in quota Description
Physical size Total on-disk space consumed to store files in OneFS. Apart from file data, this counts user metadata (for example, ACLs and user-specified extended attributes) and data protection overhead. Accounts for on-premise capacity consumption with data protection. File data blocks (non-sparse regions) + IFS metadata (ACLs, ExAttr, inode) + data protection overhead
File system logical size Approximation of disk usage on other systems by ignoring protection overhead. The space consumed to store files with 1x protection. Accounts for on-premise capacity consumption without data protection. File data blocks (non-sparse regions) + IFS metadata (Acls, ExAttr, inode)
Application logical size Apparent size of file that a user/application observes. How an application sees space available for storage regardless of whether files are cloud-tiered, sparse, deduped, or compressed. It is the offset of the file's last byte (end-of-file). Application logical size is unaffected by the physical location of the data, on or off cluster, and therefore includes CloudPools capacity across multiple locations. Accounts for on-premise and off-premise capacity consumption without data protection. The physical size and file system logical size quota metrics count the number of blocks required to store file data (block-aligned). The application logical size quota metric is not block-aligned. In general, the application logical size is smaller than either the physical size or file system logical size, as the file system logical size counts the full size of the last block of the file, whereas application logical size considers the data present in the last block. However, application logical size will be higher for sparse files.

Most quota configurations do not need to include data protection overhead calculations, and therefore do not need to include physical space, but instead can include logical space (either file system logical size, or application logical size). If you do not include data protection overhead in usage calculations for a quota, future disk usage calculations for the quota include only the logical space that is required to store files and directories. Space that is required for the data protection setting of the cluster is not included.

Consider an example user who is restricted by a 40 GB quota that does not include data protection overhead in its disk usage calculations. (The 40 GB quota includes file system logical size or application logical size.) If your cluster is configured with a 2x data protection level and the user writes a 10 GB file to the cluster, that file consumes 20 GB of space but the 10GB for the data protection overhead is not counted in the quota calculation. In this example, the user has reached 25 percent of the 40 GB quota by writing a 10 GB file to the cluster. This method of disk usage calculation is recommended for most quota configurations.

If you include data protection overhead in usage calculations for a quota, future disk usage calculations for the quota include the total amount of space that is required to store files and directories, in addition to any space that is required to accommodate your data protection settings, such as parity or mirroring. For example, consider a user who is restricted by a 40 GB quota that includes data protection overhead in its disk usage calculations. (The 40 GB quota includes physical size.) If your cluster is configured with a 2x data protection level (mirrored) and the user writes a 10 GB file to the cluster, that file actually consumes 20 GB of space: 10 GB for the file and 10 GB for the data protection overhead. In this example, the user has reached 50 percent of the 40 GB quota by writing a 10 GB file to the cluster.

NOTE Cloned and deduplicated files are treated as ordinary files by quotas. If the quota includes data protection overhead, the data protection overhead for shared data is not included in the usage calculation.

You can configure quotas to include the space that is consumed by snapshots. A single path can have two quotas applied to it: one without snapshot usage, which is the default, and one with snapshot usage. If you include snapshots in the quota, more files are included in the calculation than are in the current directory. The actual disk usage is the sum of the current directory and any snapshots of that directory. You can see which snapshots are included in the calculation by examining the .snapshot directory for the quota path.

NOTE Only snapshots created after the QuotaScan job finishes are included in the calculation.

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