PowerScale OneFS 9.5.0.0 Web Administration Guide

When device failures result in data loss (for example, three drives or two nodes in a +2:1 policy), enabling this setting ensures that intact data is still accessible.

When this setting is disabled, the directory that contains a file pool is protected according to your protection-level settings, but the devices used to store the directory and the file may not be the same. There is potential to lose nodes with file data intact but not be able to access the data because those nodes contained the directory.

As an example, consider a cluster that has a +2 default file pool protection setting and no additional file pool policies. OneFS directories are always mirrored, so they are stored at 3x, which is the mirrored equivalent of the +2 default.

This configuration can sustain a failure of two nodes before data loss or inaccessibility. If this setting is enabled, all directories are protected at 4x. If the cluster experiences three node failures, although individual files may be inaccessible, the directory tree is available and provides access to files that are still accessible.

In addition, if another file pool policy protects some files at a higher level, these too are accessible in the event of a three-node failure.

• When disabled, restricts per-file metadata to the storage pool policy of the file, except in the case of spillover. This is the default setting.
• When enabled, allows per-file metadata to use the SSDs in any node pool.

If nodes are added to or removed from a cluster, and the SSD thresholds are no longer satisfied, GNA becomes inactive. GNA remains enabled, so that when the SSD thresholds are met again, GNA is reactivated.

OneFS manages all cache levels to provide optimal data protection, availability, and performance. In case of a power failure, the data on L3 cache is retained and still available after power is restored.

--virtual-hot-spare-hide-spare

--virtual-hot-spare-limit-drives

--virtual-hot-spare-limit-percent

Reserves a minimum amount of space in the node pool that can be used for data repair in the event of a drive failure.

To reserve disk space for use as a virtual hot spare, select from the following options:

• Ignore reserved disk space when calculating available free space. Subtracts the space reserved for the virtual hot spare when calculating available free space.

• Deny data writes to reserved disk space. Prevents write operations from using reserved disk space.

• VHS Space Reserved. You can reserve a minimum number of virtual drives (1-4), as well as a minimum percentage of total disk space (0-20%).

If you configure both the minimum number of virtual drives and a minimum percentage of total disk space when you configure reserved VHS space, the enforced minimum value satisfies both requirements.

If this setting is enabled and Deny new data writes is disabled, it is possible for the file system utilization to be reported at more than 100%.

--spillover-enabled

Specifies how to handle write operations to a node pool that is not writable.

• When enabled, redirects write operations from a node pool that is not writable either to another node pool or anywhere on the cluster (the default).
• When disabled, returns a disk space error for write operations to a node pool that is not writable.

--spillover-anywhere

When spillover is enabled, but it is important that data writes do not fail, select anywhere for the Spillover Data Target setting, even if file pool policies send data to specific pools.

When Apply to files with manually-managed protection is enabled, overwrites any protection settings that were configured through File System Explorer or the command-line interface.

When Apply to files with manually-managed I/O optimization settings is enabled, overwrites any I/O optimization settings that were configured through File System Explorer or the command-line interface