On the MarkLogic Monitoring Dashboard, the free space shows as full. According to the MarkLogic documentation, this refers to the amount of free space remaining on the disk after accounting for the forest’s reserved space. The file system location shown above the graph is full. Even after clearing a high-volume forest, the free space still shows as zero. I’d like to clarify how this free space is calculated and understand what steps I can take to free up more space.
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The monitoring dashboard calculations and warnings need improvement. It’s calculating a worst case scenario in which all stands are merging, and may be over-estimating how much space is required. Therefore the “reserve” and “free” estimations may not be reliable, depending upon which version of MarkLogic you are using.
There have been updates/improvements made in 11.3.0.
MLE-548 The monitoring dashboard capacity calculation and warning in the disk-space monitoring dashboard is incorrect.
When a stand is merging, you need to be able to hold the original stand and the newly merged stand, and then once the newly merged stand is written the old stand is deleted. The maximum size of a stand is limited by the merge-max-size setting. So, at a minimum you would need merge-max-size available to ensure that at least one stand can merge, and the size of the database free if you wanted to ensure that all stands could merge at once (not likely).
You want to have enough room for multiple stands to be able to merge concurrently. And of course, you want to have some free space available to accommodate growth and any indexes or changes that might increase the storage footprint.