Oracle FAQ Your Portal to the Oracle Knowledge Grid

Home -> Community -> Usenet -> c.d.o.server -> Re: Oracle Parallel Server

Re: Oracle Parallel Server

From: Pete Sharman <>
Date: 11 Jul 2002 08:55:25 -0700
Message-ID: <>

In article <agk0mn$pqn$>, "Jay" says...
>What are the advantages of a clustered file system over raw devices? I
>haven't had the opportunity to work with either.
>I've been looking around the web for explanations/descriptions of clustered
>file system but can't find anything good. It seems veritas makes one. But
>is it a piece of software, hardware, or both. You mention compaq makes one
>Is setting up and administering a RAC significantly harder than a single
>instance database.
>I think I'm struggling because I don't understand the pieces and how they
>fit together. Would someone care to describe how the whole thing is put

Dang, that's asking a bit much! ;)

THe best thing I can suggest is to read the RAC Concepts manual. The RAC/OPS documentation has been the best written part of the doc (IMHO) in the last couple of releases.

The difference between RAC on hardware that supports clustered file systems (CFS) and hardware that doesn't is relatively simple, but only applies to Unix environments and Win2K (i.e. not a concern on VMS). Unix cannot share files unless they're placed on raw devices. Since OPS and RAC both have a shared disk architecture, that means that the database files used to have to be on raw devices. Some people have issues with that, finding them harder to manage. I don't believe that's true, though. Others think raw devices are great for performance. They may be, but it's not a hard and fast fact. I remember an otherwise intelligent DBA telling me that raw devices ALWAYS improved performance by 30%. I couldn't convince him otherwise, so I let him go on his unenlightened way. Yes you can improve performance, yes it can be by 30% but no it's not ALWAYS that way.

Back to CFS. When you install RAC, here's what happens. If your cluster is configured properly (i.e. the cluster software is working), the installer automatically picks up that it's running on a cluster and asks what nodes (other than the local one) you want to install RAC on. You can choose one or all of the available nodes. If you are using a CFS, then the kernel can be installed there and that's it. If you're not, the kernel installs once locally, and then behind the scenes does an rcp to install on every other node you've chosen.

So in summary what a CFS gives you is two things:

  1. A simpler install - the rcp can fail if the oracle account logins are different on each node (don't laugh, I've seen it!)
  2. The ability to put your database files on the CFS (for Compaq anyway), where they can easily be seen and hopefully there's less chance of a dumb SYSADMIN mounting a raw device that had your database files on it (EOD - end of database).

If you're running on 9.2, then Oracle can provide its own CFS. I think this applies for Windows only though (and maybe Linux).

>"Pete Sharman" <> wrote in message
>> In article <agijfd$j3j$>, "Jay says...
>> >
>> >Hi,
>> >
>> >My client may want to implement parallel server. They are (sorta) an HP
>> >shop. But Oracle has been promoting RACs on Linux as a very cost
>> >solution. Anyone ever implement upon Linux, Pros/Cons? Other platforms
>> >Pros/Cons?
>> >
>> >Thanks
>> >Jay
>> >
>> >
>> And so it is. One of the real benefits of the Linux configs is that there
>> certified configurations that you can use "out of the box". Depending on
>> vendor you buy them from, you can either plug in the cluster and RAC is
>> preloaded, or part of the purchase cost may include the time of a
>> (not necessarily an Oracle one) to install and configure RAC. About the
>> con I can think of is that Linux hasn't had the long history of supporting
>> clustering in the way some other Unix platforms have.
>> If you need to install everything yourself, then I think Compaq is a good
>> (note this is purely a personal thing, not an Oracle recommendation)
>because it
>> has a clustered file system. Sun does too, but it's not supported for the
>> database files (performance isn't good enough), and I know other vendors
>> been working on them for a while, but remember Compaq bought Digital which
>> course had clusters centuries ago (in computing time anyway). It will be
>> interesting to see how HP uses the Compaq/Digital technology in this area.
>> Having said that, I haven't really heard anything against any of the other
>> Unix players. HP-UX and AIX both work perfectly well with RAC too. You
>> even investigate VMS, though it tends to lag release timeframes compared
>to Unix
>> environments.
>> Win2K I can't say too much about, because it's not something I've had a
>lot of
>> experience with in the clustered environment. I'm still not convinced
>it's as
>> robust as Linux, Unix or VMS, anyway.
>> HTH. Additions and corrections welcome.
>> Pete
>> SELECT standard_disclaimer, witty_remark FROM company_requirements;

HTH. Additions and corrections welcome.


SELECT standard_disclaimer, witty_remark FROM company_requirements; Received on Thu Jul 11 2002 - 10:55:25 CDT

Original text of this message