| From: | Christoph Berg <myon(at)debian(dot)org> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Bernd Helmle <mailings(at)oopsware(dot)de>, Michael Paquier <michael(at)paquier(dot)xyz>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Enable data checksums by default |
| Date: | 2019-04-01 08:16:47 |
| Message-ID: | 20190401081647.GB13726@msg.df7cb.de |
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| Lists: | pgsql-hackers |
Re: Tomas Vondra 2019-03-30 <20190330192543(dot)GH4719(at)development>
> I have not investigated the exact reasons, but my hypothesis it's about
> the amount of WAL generated during the initial CREATE INDEX (because it
> probably ends up setting the hint bits), which puts additional pressure
> on the storage.
>
> Unfortunately, this additional cost is unlikely to go away :-(
If WAL volume is a problem, would wal_compression help?
> Now, maybe we want to enable checksums by default anyway, but we should
> not pretent the only cost related to checksums is CPU usage.
Thanks for doing these tests. The point I'm trying to make is, why do
we run without data checksums by default? For example, we do checksum
the WAL all the time, and there's not even an option to disable it,
even if that might make things faster. Why don't we enable data
checksums by default as well?
Christoph
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