Sum of written buffers bigger than allocation?

Hi All!

First time I see that the sum of written buffers:
3765929+878326121 = 882092050 = select
pg_size_pretty(882092050::numeric*8192) = 6730 GB

is bigger than buffers_alloc value in pg_stat_bgwriter view:
buffers_alloc         | 20426161 = 156 GB


buffers_checkpoint    | 878599316
buffers_clean         | 0
maxwritten_clean      | 0
buffers_backend       | 3766409
buffers_backend_fsync | 0
buffers_alloc         | 20426161


It's kinda mysterious... Any explanations?
Does it mean that the same buffers were written over and over again?





--
Sent from: http://www.postgresql-archive.org/PostgreSQL-general-f1843780.html