blobstore Blob count and Total size are sometimes incorrect

In the Nexus Blob stores the Blob count and Total size shows the wrong information. Our total disk space for the nexus is about 300GB. but Nexus shows the total space about 900GB which is very misleading

Diagnosis

Blobstore metrics could be incorrect for a variety of reasons:

Edge Cases:

• an existing bug
• Manual deletion of stuff from the disk
• system crashes at inopportune times

Other:

For users who have a blob store with soft-deleted and not-yet-compacted blobs that then update to latest NXRM version and compact the blob store with that, the previously soft-deleted blobs are double-counted: They were removed from the metrics by the old code during soft-delete, then again by the new code during hard-delete/compact, resulting in metrics that are too low in numbers.

Possible Remedy

Develop a supported procedure to bring blobstore metrics back in sync for each type of supported blobstore type.