Re: SCSI vs. IDE performance test

ahhh. "lies about write order" is the phrase that I was looking for. That
seemed to make sense but I didn't know if I could go directly from "lying
about fsync" to that. Obviously I don't understand exactly what fsync is
doing. I assume this means that if you were to turn fsync off you would get
considerably better performance but introduce the possibility of corrupting
the files in your database.

Thank you. This makes a lot more sense now.

----- Original Message -----
From: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Rick Gigger" <rick(at)alpinenetworking(dot)com>
Cc: <pgsql-general(at)postgresql(dot)org>
Sent: Monday, October 27, 2003 3:39 PM
Subject: Re: [GENERAL] SCSI vs. IDE performance test

> "Rick Gigger" <rick(at)alpinenetworking(dot)com> writes:
> > It seems to me file system journaling should fix the whole problem by
giving
> > you a record of what was actually commited to disk and what was not.
>
> Nope, a journaling FS has exactly the same problem Postgres does
> (because the underlying "WAL" concept is the same: write the log entries
> before you change the files they describe). If the drive lies about
> write order, the FS can be screwed just as badly. Now the FS code might
> have a low-level way to force write order that Postgres doesn't have
> access to ... but simply uttering the magic incantation "journaling file
> system" will not make this problem disappear.
>
> regards, tom lane
>
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