FileCount and DeleteCount were int, so each cost a word on every replica the
master holds. A volume caps at 30GB on a 4-byte-offset build and 8TB on a
5-byte one, and neither holds 4.29 billion needles.
That takes VolumeInfo from 120 bytes to 112, which is its own size class rather
than rounding up into the 128 one, so a replica costs 135.7 bytes in the map
instead of 151.7 -- about 25MB across the 1.6M replicas in a cluster the size
of the one this came from.
Counts are narrowed where they are read rather than assigned across, so a
report claiming more than a volume can hold pins at the ceiling instead of
wrapping to a small number.
Chris Lu
980471c818