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Re: Disk Failure Scenarios

From: "Michael Artz" <mlartz(at)gmail(dot)com>
To: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Disk Failure Scenarios
Date: 2006-04-27 09:46:36
Message-ID: e9c163070604270246j5d4c4fefi42bbdfb01518eccd@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-general
> > -Disk 2: If the transaction log dies, all changes since the last
> > checkpoint are lost, right?  Again, if I set up an empty pg_xlog
> > directory somewhere else, the DB should run just fine, right?
>
> No, because there's no way to know what state the data pages are in.
> Data may have made it to disk, may not have, partial page write, etc...


As far as I understand it, data is only written to the WAL except when the
WAL is checkpointing, right?  So if your WAL disk crashes and you aren't int
the middle of a checkpoint, there is a chance that you would just lose data
since the last checkpoint.  Am I missing something?

Now the real question is: why are you trying to run without raid?


I have a single, very fast disk lying around, and I was just wondering what
parts of the DB I could "safely" put on it.  I was thinking either the WAL
or and index.  I have essentially 15 10K drives and 1 15K drive, and don't
quite know what to do with it.

-Mike

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