Re: Redesigning checkpoint_segments

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Redesigning checkpoint_segments
Date: 2015-02-05 21:52:55
Message-ID: CA+TgmoZ1dYS6cY7OZXXSDsme=eHXGGM0Gyg4Y36NDz4Aa1dqfQ@mail.gmail.com
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>>> Default of 4 for min_wal_size?
>>
>> I assume you mean 4 segments; why not 3 as currently? As long as the
>> system has the latitude to ratchet it up when needed, there seems to
>> be little advantage to raising the minimum. Of course I guess there
>> must be some advantage or Heikki wouldn't have made it configurable,
>> but I'd err on the side of keeping this one small. Hopefully the
>> system that automatically adjusts this is really smart, and a large
>> min_wal_size is superfluous for most people.
>
> Keep in mind that the current is actually 7, not three (3*2+1). So 3
> would be a siginficant decrease. However, I don't feel strongly about
> it either way. I think that there is probably a minimum reasonable
> value > 1, but I'm not sure what it is.

Good point. OK, 4 works for me.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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