OCFS2…

I’m nearing the end of my “I wonder what RAC is like on other platforms?” phase. I ran through a basic setup of a cluster file system using OCFS2, just to prove it worked:

OCFS2 On Linux

As I say in the article, the only reason to use it as far as I can see is to provide a shared location or UTL_FILE and external table operations. I can’t see the point in using it for the OCR location or voting disk as raw devices work fine and it’s not recommended for sharing datafiles…

I guess it’s nice to know it’s there if I ever need it 🙂

Cheers

Tim…

Author: Tim...

DBA, Developer, Author, Trainer.

23 thoughts on “OCFS2…”

  1. Normally I agree with most of your blog stuff but had to give my 2 pence worth.

    How can you say OCFS is not recommended for datafiles?!!

    Yes Oracle’s asm is the preferred method at 10g, but it doesn’t make OCFS redundant. Indeed, as I’m sure you’re aware the sole reason that OCFS was written in the first place was to provide a cluster file system for Linux for RAC to run on, for those who didn’t want to use raw devices.

    Bazza

  2. [my opinion]
    – ASM is the way to go as far as database file storage is concerned.

    – You wouldn’t want to mix database files and non-database files on a single mount point if you could help it.

    – If you are going to give a whole mount point over to ASM, what is the point in adding another layer of complexity by using OCFS. It can only make the system slower! You might as well use a raw device directly, or via ASMLib.

    – With that in mind, using OCFS for datafiles is not the recommended route.
    [/my opinion]

    Each to their own.

    Cheers

    Tim…
    PS.

  3. I concur you wouldn’t want to mix files on the same mountpoint.

    What I would argue is , if you are going to have to use OCFS anyway (for OCR and voting disk) why, then bother adding to the complexity of managing the system by using ASM? 😉

    I have to confess my knowledge of ASM is rudimentary at best, but to unequivocally state that OCFS is not recommended, is totally misleading.

    Each to their own indeed 😉

    Bazza

  4. First, you don’t need to use OCFS2 at all. You can put the OCR location and voting disk on raw devices.

    A cursory scan of the net will show you that many people have had problems using both OCFS(2) and ASMLib due to numerous bugs. None of these would have happened if people had used raw devices.

    There are numerous statements on the net, by Oracle and others, suggesting that ASM is the preferred storage solution for RAC, and possible for single node installations also.

    Several people, including Howard Rogers and Jonathan Lewis have expressed their preference to avoid the use of OCFS2 in favour of ASM and raw devices.

    I think the best comment I’ve seen regarding both OCFS2 and ASMLib is,

    “Both are chock full of problems and ‘de-emphasized'”

    I think that says it all. Even Oracle aren’t pushing them so hard these days. ASM is the future 🙂

    But hey, each to their own.

    Cheers

    Tim…

  5. Yes you are right on everything on your last main post, I dare not contest anything there! You kinda missed my point on asm making the system, as a whole, more complex to manage. Just managing OCFS (should you choose to use it) or manage ASM AND OCFS, well the math speaks for itself.

    But, and its a big but, my original post was to contradict your statement about OCFS not being recommended. That was and is utterly misleading. OCFS was originally written for people who did not want to manage RAW devices, and to put database files on!

    OCFS 2 lets not forget, will enable the oracle home to be shared between. So, if you want to use OCFS, for it benefits, then I would argue there is no need to use ASM…

    I’ll get off my soapbox now…

    Bazza

    P.S. On a separate note, a bugbear of mine is unquantifed quotes…its the lawyer in me! 😉

  6. Hi.

    Fair enough 🙂

    I guess the real issue with raw paritions use to be you needed one per file and managing that was a real pain. Now, if you use ASM you just lump all your disks into one or more disk groups and let ASM manage the files. As a ersult, most of the problems associated with raw paritions have gone away. Hence, my point that OCFS(2) is no longer necessary.

    There are a number of issue asociated with a shared Oracle Home (installation directory). One of which is the rolling patches (that don’t really exist :)) won’t work with them. I use a shared Oracle Home on Tru64, and after trying Linux and Windows I can safely say that given the choice I would not share the Oracle Home myself!

    Anyway, enough of my ranting 🙂

    You are correct. I should be a bit moer careful with the way I phrase things and I’ll try to do so in future. I guess the ASM vs OCFS is just one of those holy wars tat will rage on for a few years 🙂

    Cheers

    Tim…

  7. Guys,
    I have been testing 10g on Linux for the last year with all different options.
    Regarding the storage choise “ASM or OCFS2”, I would definatelly pick OCFS2!

    ASM adds a layer b/n the OS and Oracle. Same with ocfs2, but ocfs has smaller footprint.
    ASM is easy to administer. So is ocfs2. The later is even easier to administer is is is visible through the OS.
    This will allow you later on to easily manage RMAN backup files for instance. Or dump db object onto the shared FS and be able to
    manipulate it, etc.
    ASM is visible through Oracle only. OCFS2 from everywhere.
    I have had more trouble with ASM than OCFS2 (though OCFS1 was quite buggy at the time).
    I am not confronting with your opinions. Just sharing my experience.

    Cheers
    Ivo

  8. Hi.

    It’s good to hear different opinions, so don’t worry about “confronting with your opinions” 🙂

    I think the thing to remember here is Oracle see ASM as the future of storage for the Oracle database. It wouldn’t suprise me if in a couple of versions time you have no choice but to use ASM. As a result, it pays to get into it sooner, rather than later. At least from a testing point of view.

    For now, you should use he technology you are happiest with. Both methods are supported, so go for it 🙂

    Cheers

    Tim…

  9. “ASM is not a heavy layer:

    http://www.freelists.org/archives/oracle-l/05-2006/msg00367.html

    …that is a reference to a post I did on ASM. ASM is not in the
    I/O code path, that is true, but that doesn’t mean it is some panacea.
    It is a partial solution to a retiring problem–provisioning RAW partitions
    from a SAN. ASM has no problem to solve when you use NAS or a functional
    general-purpose CFS. I have a bit of such topics on my blog:

    kevinclosson.wordpress.com

  10. Hi clearly can any one tell me why is that not preferable to use OCR and voting disk using ASM than ocfs and other cluster ware

    plz can anyone be soon in replying me

  11. Hi.

    If you check out the installation process, you will see that the clusterware must be installed before you can install ASM.

    The clusterware needs the voting disk and OCR location and it is installed before ASM is present, so that explains whay you can’t use ASM. 🙂

    Cheers

    Tim…

  12. Tim ya but i want to know that why cant we go for ASM for storing those two files rather why we go for others

    And with ur ans cant we install ASM before we install the cluster ware if so why cant we ?

    plz explain me brief i am really in need of that

  13. Tim,

    What are your thoughts on putting OCR/Voting onto OCFS2 instead of RAW? Considering that RAW devices are being depreciated by ORACLE:

    From Oracle RDBMS version 10.2.0.2.0 and higher, block devices can be
    accessed via any of the following methods and utilized by the RDBMS:

    * Direct block device access
    * ASMLib mapped devices
    * OCFS2 devices
    * LVM2 mapped devices (single instance only)”

    REFERENCE:
    Note:357492.1 Linux 2.6 Kernel Deprecation Of Raw Devices

    Thanks

  14. Hi.

    OCFS2 is fine. Remember also, that in 11gR2 you will be able to store OCR configuration and voting disks in ASM, so you don’t have to use RAW or OCFS2.

    Cheers

    Tim…

  15. I know that oracle pushes ASM rather than ocfs2 but I think that this may not be a good decision and at the end oracle will loose lots of client to veritas cfs.

    Ocfs2 has it’s own strong point on top of ASM like easy of use. Specially, company which need database cloned regular bases between production and QA system need to asign extra staging area to take backset out of ASM volume before the transfer. And so far ASM provide very limited functions for this kinds of scenarios.

    So, I hope that oracle enhance their ASM to provide better interaction to the outside of ASM and also between the ASM on both local and remote servers.

  16. Hi,
    In my opinion, ASM adds the manageability advantage over the performance advantage of raw file systems. Online space management is one important feature to consider.
    But in our RAC setup, we are exploring possibilities of adding OCFS2 along with ASM, the primary reason being, the tape library that we use cannot read the backups directly from ASM. RMAN would be better off using OCFS2 so that the downstream backup possibilities are much wider and easier from an OCFS2 filesystem to other devices/systems.

    -Ganesh

  17. Hi.

    Please don;t use OCFS2 and RAC together. They are two different clustering frameworks. As a result, they often trip each other up. Personally I would avoid combining at all costs. Use an NFS mount for shared disks, or if you are using 11gR2 use ACFS.

    Cheers

    Tim…

  18. I am building 11gR2 RAC using ASM on Linux servers. Being EMC data domain(DD) our primary backup storage, there are a few options to take in terms of FRA and ASM. One easy option is define FRA on ASM as Oracle recommends. But in that case as database is backed to FRA/ASM, DD cannot be used. 2nd option is to backup database into DD, non-FRA area, which is not a great idea. 3rd option is define FRA on a cluster file system such as GFS, ACFS, OCFS2, etc and softlink FRA backup directory to NFS mounted DD directory. It sounds complicated but, we use FRA and have backup on DD. The problem is that ACFS is dropped because it is not supported for database files (control files, archivelog files, redo log files which are placed in FRA). GFS is dropped as it requires another redhat clusterware. OCFS2 is the only option for now. My only concern is Oracle’s future strategy.

  19. Hi.

    OCFS2 and RAC on a single system is a *complete* disaster. Why? Because they are competing clustering solutions. They have no knowledge of each other and will interfere with each other. Sometimes OCFS2 will have a problems and force a node restart when Clusterware is happy, and vice versa. In my opinion, they should never be used together.

    Why not use an NFS mount for the location? It’s sharable and allows you to use regular files, which seems to be what you want.

    Cheers

    Tim…

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