Hi Team,

With storing of Lucene index files within DataStore our usage pattern
of DataStore has changed between JR2 and Oak.

With JR2 the writes were mostly application based i.e. if application
stores a pdf/image file then that would be stored in DataStore. JR2 by
default would not write stuff to DataStore. Further in deployment
where large number of binary content is present then systems tend to
share the DataStore to avoid duplication of storage. In such cases
running Blob GC is a non trivial task as it involves a manual step and
coordination across multiple deployments. Due to this systems tend to
delay frequency of GC

Now with Oak apart from application the Oak system itself *actively*
uses the DataStore to store the index files for Lucene and there the
churn might be much higher i.e. frequency of creation and deletion of
index file is lot higher. This would accelerate the rate of garbage
generation and thus put lot more pressure on the DataStore storage
requirements.

Any thoughts on how to avoid/reduce the requirement to increase the
frequency of Blob GC?

One possible way would be to provide a special cleanup tool which can
look for such old Lucene index files and deletes them directly without
going through the full fledged MarkAndSweep logic

Thoughts?

Chetan Mehrotra

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