In principle, there’s no limit on the number of tables in a MapR cluster. Since tables are composed of many files, you might want to place tables into multiple volumes.
A table is composed of tablets. By default a 4GB tablet is composed of 1000-2000 segments, which are between 1 and 6 files each. There are about 10,000 files per tablet (or per 4GB). Ideally, a volume should have fewer than 10-50 million files. This approximation allows for 1000-5000 tablets, or 4-20TB of table data, in one volume. This doesn’t mean a single table is limited to 20TB. It means that you might want to consider using multiple volumes if you have multiple small tables.
Small tables don't have size restrictions. MapR-DB can handle many, many small tablets without issue. Of course, a small table is composed of very few tablets. If necessary (for performance, for example), you can force a small table to be composed of more tablets, by configuring the tablet size. The lower bound is 256MB.
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