Re: extremly low memory usage

From: Marko Ristola
Subject: Re: extremly low memory usage
Date: ,
Msg-id: 43071162.6050405@kolumbus.fi
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In response to: Re: extremly low memory usage  (Dan Harris)
Responses: Re: extremly low memory usage  (Michael Stone)
List: pgsql-performance

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extremly low memory usage  (Jeremiah Jahn, )
 Re: extremly low memory usage  (John A Meinel, )
  Re: extremly low memory usage  (Jeremiah Jahn, )
   Re: extremly low memory usage  (John Arbash Meinel, )
 Re: extremly low memory usage  (Jeff Trout, )
  Re: extremly low memory usage  (Jeremiah Jahn, )
   Re: extremly low memory usage  (John Arbash Meinel, )
    Re: extremly low memory usage  (Ron, )
    Re: extremly low memory usage  (Jeremiah Jahn, )
     Re: extremly low memory usage  (John A Meinel, )
      Re: extremly low memory usage  (Ron, )
       Re: extremly low memory usage  (John A Meinel, )
        Re: extremly low memory usage  (Jeremiah Jahn, )
         Re: extremly low memory usage  (Ron, )
          Re: extremly low memory usage  (Jeremiah Jahn, )
        Re: extremly low memory usage  (Jeremiah Jahn, )
         Re: extremly low memory usage  (John A Meinel, )
          Re: extremly low memory usage  (Jeremiah Jahn, )
           Re: extremly low memory usage  (Ron, )
           Re: extremly low memory usage  (John A Meinel, )
         Re: extremly low memory usage  (Dan Harris, )
          Re: extremly low memory usage  (Marko Ristola, )
           Re: extremly low memory usage  (Michael Stone, )
            Re: extremly low memory usage  (Tom Lane, )
             Re: extremly low memory usage  (Marko Ristola, )
          Re: extremly low memory usage  (Michael Stone, )
      Re: extremly low memory usage  (Jeremiah Jahn, )
       Re: extremly low memory usage  (John A Meinel, )
        Re: extremly low memory usage  (Jeremiah Jahn, )
         Re: extremly low memory usage  (Ron, )
          Re: extremly low memory usage  (John A Meinel, )
           Re: extremly low memory usage  (Jeremiah Jahn, )
            Re: extremly low memory usage  (John A Meinel, )
            Re: extremly low memory usage  (Ron, )
             Re: extremly low memory usage  (William Yu, )
             Re: extremly low memory usage  (Jeremiah Jahn, )
              Re: extremly low memory usage  (John A Meinel, )
 Re: extremly low memory usage  (Ron, )
 Re: extremly low memory usage  (Ron, )

Dan Harris wrote:

> From my recent experiences, I can say ext3 is probably not a great
> choice for Pg databases.  If you check the archives you'll see
> there's a lot of discussion about various journalling filesystems and
> ext3 usually(always?) comes up on the bottom as far as performance
> goes.  If you insist on using it, I would at least recommend the
> noatime option in fstab and using data=writeback to get the faster


Based on my knoledge, Ext3 is good with keeping filesystem integrity AND
data integrity while
pressing the reset button.
However, by selecting data=writeback, you gain more speed, but you risk the
data integrity during a crash: Ext3 garantees only filesystem integrity.

This means with database transaction logs: The last transactions are not
guaranteed to be written into the hard drives during a hardware reset,
meaning of a loss of some committed transactions.

Reiserfs is known to do things this false way also.
Is there a way with a Reiserfs filesystem to fulfill both
filesystem AND data integrity requirements nowadays?

See for example "man mount" to see the effects of data=journal,
data=ordered(default) and
data=writeback for Ext3. Only the writeback risks data integrity.

Ext3 is the only journaled filesystem, that I know that fulfills
these fundamental data integrity guarantees. Personally I like about
such filesystems, even though it means less speed.

Marko Ristola





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