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Date: Thu, 04 Aug 2011 12:03:23 +0800
From: Craig Ringer <ringerc@ringerc.id.au>
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To: pgsql-performance@postgresql.org
Subject: Re: Parameters for PostgreSQL
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On 04/08/11 11:42, Jayadevan M wrote:
> Hello,
>
> >The most important spec has been omitted. What's the storage subsystem?
> We have storage on SAN, RAID 5.

RAID 5? That's *really* not ideal for database workloads, either Pg or
Oracle, unless your RAID 5 storage backend has enough battery-backed
write cache to keep huge amounts of writes in RAM and reorder them
really effectively.

I hope each RAID 5 LUN is only across a few disks and is layered with
RAID 1, though. RAID 5 becomes less reliable than using a single disk
when used with too many HDDs, because the probability of a double-disk
failure becomes greater than that of a single standalone disk failing.
After being bitten by that a few times, these days I'm using RAID 6 in
most cases where RAID 10 isn't practical.

In any case, "SAN" can be anything from a Linux box running an iSCSI
target on top of a RAID 5 `md' software RAID volume on four 5400RPM
HDDs, right up to a giant hundreds-of-fast-disks monster filer full of
dedicated ASICs and great gobs of battery backed write cache DRAM. Are
you able to be any more specific about what you're dealing with?

>  
> > > We are suing weblogic.
> >           ^^^^^
> > Best. Typo. Ever.
> >
> > I hear most people who use it want to, you're just brave enough to
> do it :-P
> I wish I could make a few millions that way.
>
>
> Thank you for all the replies. The first step is, of course, to
> migrate the data. I am working with ora2pg for that. I assume creating
> files with 'COPY' to work as input for PostgreSQL is the right
> approach? We don't have many stored procedures or packages. So that
> part should be OK.



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    On 04/08/11 11:42, Jayadevan M wrote:
    <blockquote
cite="mid:OFB5D52348.1A6D34E9-ON652578E2.00137B30-652578E2.001450FD@ibsplc.com"
      type="cite">
      <meta http-equiv="Context-Type" content="text/html;
        charset=US-ASCII">
      <tt> Hello, </tt> <br>
      <tt> <br>
        &gt;The most important spec has been omitted. What's the storage
        subsystem? </tt> <br>
      <tt> We have storage on SAN, RAID 5.</tt><br>
    </blockquote>
    <br>
    RAID 5? That's *really* not ideal for database workloads, either Pg
    or Oracle, unless your RAID 5 storage backend has enough
    battery-backed write cache to keep huge amounts of writes in RAM and
    reorder them really effectively.<br>
    <br>
    I hope each RAID 5 LUN is only across a few disks and is layered
    with RAID 1, though. RAID 5 becomes less reliable than using a
    single disk when used with too many HDDs, because the probability of
    a double-disk failure becomes greater than that of a single
    standalone disk failing. After being bitten by that a few times,
    these days I'm using RAID 6 in most cases where RAID 10 isn't
    practical.<br>
    <br>
    In any case, "SAN" can be anything from a Linux box running an iSCSI
    target on top of a RAID 5 `md' software RAID volume on four 5400RPM
    HDDs, right up to a giant hundreds-of-fast-disks monster filer full
    of dedicated ASICs and great gobs of battery backed write cache
    DRAM. Are you able to be any more specific about what you're dealing
    with?<br>
    <br>
    <blockquote
cite="mid:OFB5D52348.1A6D34E9-ON652578E2.00137B30-652578E2.001450FD@ibsplc.com"
      type="cite"><tt> &nbsp;<br>
        &gt; &gt; We are suing weblogic.<br>
        &gt; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ^^^^^<br>
        &gt; Best. Typo. Ever.<br>
        &gt; <br>
        &gt; I hear most people who use it want to, you're just brave
        enough to do it :-P<br>
        I wish I could make a few millions that way. </tt> <br>
      <br>
      <br>
      <tt> Thank you for all the replies. The first step is, of course,
        to migrate the data. I am working with ora2pg for that. I assume
        creating files with 'COPY' to work as input for PostgreSQL is
        the right approach? We don't have many stored procedures or
        packages. So that part should be OK. </tt> <br>
    </blockquote>
    <br>
    <br>
  </body>
</html>

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