| From: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
|---|---|
| To: | Jim Nasby <jim(at)nasby(dot)net> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Trond Myklebust <trondmy(at)gmail(dot)com>, Bottomley James <James(dot)Bottomley(at)HansenPartnership(dot)com>, Hannu Krosing <hannu(at)2ndQuadrant(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Andres Freund <andres(at)2ndQuadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Kevin Grittner <kgrittn(at)ymail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dave Chinner <david(at)fromorbit(dot)com>, Joshua Drake <jd(at)commandprompt(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Mel Gorman <mgorman(at)suse(dot)de>, "lsf-pc(at)lists(dot)linux-foundation(dot)org" <lsf-pc(at)lists(dot)linux-foundation(dot)org>, Magnus Hagander <magnus(at)hagander(dot)net> |
| Subject: | Re: [Lsf-pc] Linux kernel impact on PostgreSQL performance |
| Date: | 2014-01-15 08:27:26 |
| Message-ID: | 52D6466E.9010803@vmware.com |
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| Lists: | pgsql-hackers |
On 01/15/2014 06:01 AM, Jim Nasby wrote:
> For the sake of completeness... it's theoretically silly that Postgres
> is doing all this stuff with WAL when the filesystem is doing something
> very similar with it's journal. And an SSD drive (and next generation
> spinning rust) is doing the same thing *again* in it's own journal.
>
> If all 3 communities (or even just 2 of them!) could agree on the
> necessary interface a tremendous amount of this duplicated technology
> could be eliminated.
>
> That said, I rather doubt the Postgres community would go this route,
> not so much because of the presumably massive changes needed, but more
> because our community is not a fan of restricting our users to things
> like "Thou shalt use a journaled FS or risk all thy data!"
The WAL is also used for continuous archiving and replication, not just
crash recovery. We could skip full-page-writes, though, if we knew that
the underlying filesystem/storage is guaranteeing that a write() is atomic.
It might be useful for PostgreSQL somehow tell the filesystem that we're
taking care of WAL-logging, so that the filesystem doesn't need to.
- Heikki
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