Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 494FBB5DC08 for ; Thu, 4 Aug 2011 02:15:47 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 15883-04 for ; Thu, 4 Aug 2011 05:15:41 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from smtp190.dfw.emailsrvr.com (smtp190.dfw.emailsrvr.com [67.192.241.190]) by mail.postgresql.org (Postfix) with ESMTP id 23BFDB5DBCA for ; Thu, 4 Aug 2011 02:15:41 -0300 (ADT) Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp19.relay.dfw1a.emailsrvr.com (SMTP Server) with ESMTP id E206D3C8460; Thu, 4 Aug 2011 01:15:40 -0400 (EDT) X-Virus-Scanned: OK Received: by smtp19.relay.dfw1a.emailsrvr.com (Authenticated sender: adarsh.sharma-AT-orkash.com) with ESMTPSA id BFB7A3C8199; Thu, 4 Aug 2011 01:15:39 -0400 (EDT) Message-ID: <4E3A2AFD.1090106@orkash.com> Date: Thu, 04 Aug 2011 10:45:41 +0530 From: Adarsh Sharma User-Agent: Thunderbird 2.0.0.22 (X11/20090625) MIME-Version: 1.0 To: Craig Ringer CC: pgsql-performance@postgresql.org Subject: Re: Parameters for PostgreSQL References: <4E373D76.9020800@postnewspapers.com.au> <4E3A1A0B.5090809@ringerc.id.au> In-Reply-To: <4E3A1A0B.5090809@ringerc.id.au> Content-Type: multipart/alternative; boundary="------------030407050904070501080509" X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.899 tagged_above=-10 required=5 tests=BAYES_00=-1.9, HTML_MESSAGE=0.001 X-Spam-Level: X-Archive-Number: 201108/44 X-Sequence-Number: 44491 This is a multi-part message in MIME format. --------------030407050904070501080509 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I think RAID 10 is best among all the RAID Levels. Thanks Craig Ringer wrote: > 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. > > --------------030407050904070501080509 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit I think RAID 10 is best among all the RAID Levels.


Thanks


Craig Ringer wrote:
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.



--------------030407050904070501080509--