broken blobs after migration from OrientDB to H2

[harridu]

• What problem are you trying to solve?
  After the migration from OrientDB to H2 using Nexus 3.70.3-01 (and its migration tool) all blob stores had the same size. Before (using OrientDB):
  

After (using H2):

Of course Nexus complained loudly because several blobs seem to have exceeded their quotas. Others shrunk alot,

• Do you have a workaround you are using at present?
  No, I am stuck with the migration. This effect is not mentioned in the migration guide, AFAICT, so it is quite alarming. Migration to JDK17 and a newer Nexus version has been stopped. Fortunately it is a stage system, cloned from the master.

• What feature or behavior is this required for?
  Migration from Nexus 3.70.3 to 3.74, JDK upgrade

• How could we solve this issue? (Not knowing is okay!)

• Tell us about your Nexus Repository deployment: what version, operating system, and database are you using?
  Nexus 3.70.3-01, Debian 12, temurin-11-jdk 11.0.25.0.0+9, DB migrated from OrientDB to H2 using OpenJDK 11 (as requested), taken from Debian 11

[alexander-vie]

It seems to be mostly a display issue, storage size and blob count is the same for most repos/blobs - but not for all blobs at our site. The free space display is plausible and approximatly the same as before.

[alexander-vie]

I was able to fix it with a job run of "Repair - Recalculate blob store storage".
Inspiration was from #482 (comment)

[harridu]

After running the recalculate task blob storage seems to be fine again. The task was running for >24h, though.

I would suggest to add this to the documentation.