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For internal metadata, you should provision approximately 2 GB of disk space for every 1 million user files, as each file consumes1 KB for its inode plus additional space for at least one directory entry. This is slightly generous but provides some room for future growth and covers pathological cases where files have several hard links and/or many extended attributes.
The amount of external metadata needed is a little more complicated to estimate.
- Unmanaged file systems that do not have Metadata Archive enabled require zero external metadata space.
- Unmanaged file systems that have Metadata Archive enabled require about 1 GB of space on the HA shared file system for every 1 million user files.
- Managed file systems require about 2 GB of space on the HA shared file system for every 1 million files due to additional metadata stored in MySQL.
After you calculate the estimated usage, you must triple the number to account for special circumstances, such as a StorNext upgrade moving to a new Metadata Archive format or keeping an extra on-line copy of the MySQL database for a service-related purpose.
Below is an example calculation of external metadata:
| Description | Value |
|---|---|
| File system snfs1, managed, 50 M files | 100 GB |
| File system snfs2, unmanaged with metadata archive enabled, 50 M files | 50 GB |
| File system snfs3, unmanaged, with metadata archive disabled, 100 M files | 0 GB |
| File system snfs4, managed, 20 M files | 40 GB |
| Sub-total | 190 GB |
| Total (sub-total multiplied by 3) | 570 GB |
Additional space is required when Metadata Archive history is enabled. The amount needed depends on factors such as the number of history days configured, the worst-case rate at which files are modified, and whether the audit feature is also enabled. It is difficult to estimate ahead of time exactly how much additional usage results from when you enable Metadata Archive history. One relatively safe way to measure its impact is to set metadataArchiveDays to a very small number for a file system and monitor the disk usage of its metadata archive over a period of days. Unfortunately, to measure this way means that the file system is already running. This, in turn, means that the provisioning decision has already been made. Nevertheless, this may provide guidance on whether or not expanding external metadata on an existing system is required to enable history.
As described later, if a StorNext system outgrows the storage initially provisioned for internal or external metadata, you can add additional space.
