Re: Simplifying wal_sync_method

From: "Magnus Hagander" <mha(at)sollentuna(dot)net>
To: "Marko Kreen" <marko(at)l-t(dot)ee>
Cc: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>, "Alvaro Herrera" <alvherre(at)alvh(dot)no-ip(dot)org>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Simplifying wal_sync_method
Date: 2005-08-09 10:14:09
Message-ID: 6BCB9D8A16AC4241919521715F4D8BCE6C7852@algol.sollentuna.se
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> > That can definitly be debated. Properly maintaned on proper
> hardware,
> > it's quite reliable these days.
> > Most filesystem corruptions that happen on windows are
> because people
> > enable write caching on drives without battery backup. The
> same issue
> > we're facing here, it's *not* a problem in the fs, it's a
> problem in
> > the admin. Sure, there are lots of things that could be better with
> > ntfs, but I would definitly not call it unreliable.
>
> People enable? Isn't it the default?

I dunno about workstation OS, but on the server OSes it certainly isn't
default.

> > > 3. The probability of mediocre hardware is higher.
> >
> > I would say it's actually *lower*. If you look in the average
> > datacenter, I bet you'll find a lot more linux boxes running on
> > built-at-home-with-the-cheapest-parts boxes. Whereas your windows
> > boxes will run on HP or IBM or whatever real server-grade hardware.
> >
> > I don't know anybody who claims to run a professional business who
> > uses IDE drives in a Windows server, for example. I know
> several who
> > run linux or freebsd on it.
>
> The professional probably tests it on his own desktop. I
> don't think PostgreSQL reaches the data center before passing
> the run on desktop.

I can't speak for others, but I would always test a server product on a
server OS on server hardware. Certainly not as beefy as eventual
production server, but the same level. Otherwise the test is not fully
relevant.

> > > Why shouldn't we offer reliable option to win32?
> >
> > *we do offer a reliabel option*.
> > Same as on POSIX, we don't enable it by default for *non-server
> > hardware*.
>
> What do you mean here? AFAIK we try to be reliable on POSIX too.

AFAIK fsync is slightly safer than open_sync, because it also flushes
the metadata. We don't default to that.

> > > Options:
> > >
> > > - Win32 guy complains that PG is bit slow.
> > > We tell him to RTFM.
> >
> > What most often happens here is:
> > Win32 guy notices PG is very slow, changes to mysql or mssql.
>
> But lost database is no problem?
>

It certainly is. That's not what I'm arguing. What I'm saying is that
you shouldn't expect server grade reliabilty on desktop hardware and
desktop OS. Regardless of platform.

//Magnus

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