PowerScale OneFS Web Administration Guide

Virtual hot spare

Virtual hot spare (VHS) settings enable you to reserve disk space to rebuild the data in the event that a drive fails.

You can specify both a number of virtual drives to reserve and a percentage of total storage space. For example, if you specify two virtual drives and 15 percent, each node pool reserves virtual drive space equivalent to two drives or 15 percent of their total capacity (whichever is larger).

You can reserve space in node pools across the cluster for this purpose by specifying the following options:

• At least 1–4 virtual drives.
• At least 0–20% of total storage.

OneFS calculates the larger number of the two factors to determine the space that is allocated. When configuring VHS settings, be sure to consider the following information:

• If you deselect the option to Ignore reserved space when calculating available free space (the default), free-space calculations include the space reserved for VHS.
• If you deselect the option to Deny data writes to reserved disk space (the default), OneFS can use VHS for normal data writes. We recommend that you leave this option selected, or data repair can be compromised.
• If Ignore reserved space when calculating available free space is enabled while Deny data writes to reserved disk space is disabled, it is possible for the file system to report utilization as more than 100 percent.