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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Marc Millas <marc.millas@mokadb.com>
cc: pgsql-performance@postgresql.org
Subject: Re: 9.6 write time
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Comments: In-reply-to Marc Millas <marc.millas@mokadb.com>
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Marc Millas <marc.millas@mokadb.com> writes:
> I am looking at a postgres 9.6 on rh7
> I see that checkpoint_write_time is huge which looks quite strange as the
> average amount of data written is not that big.

checkpoint_write_time is not the amount of time spent doing I/O;
it's the elapsed wall-clock time in the write phase.  If the I/O
is being throttled because of an un-aggressive checkpoint completion
target, it could be a lot more than the actual I/O time.  What have
you got your checkpoint parameters set to?

			regards, tom lane