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10 Replies Latest reply: Jan 30, 2013 9:09 AM by mdaskalov RSS

New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible

mdaskalov Newbie
Currently Being Moderated
Hi everyone,
I would like to ask whether that latest version of Oracle Linux 6 can be used for a new installation (one that will replace Windows) to serve as that basis for Oracle RAC.
The storage is a high-end EMC Clariion.

I want to use the Unbreakable Enterprise Linux 2.
I would like to use EMC Powerpath, but it seems this is not yet available (or at list not present in the current EMC support matrix).
I want to use ASMLib, but if have to use redhat compatible kernel (so that I can use Powerpath), I will not be able to use ASMLib (AFAIK).

Does anybody has experience with this problem? What would you recommend?

I'm putting a list of possile options that I am aware of:

1. Use OEL5 with redhat compatible kernel (use Powerpath and ASMLib).
2. Use OEL6 with UEK2 kernel, but don't use Powerpath (use dm-multipath and ASMLib)
3. Use OEL6 with redhat compatible kernel (use Powerpath and don't use ASMLib, but use udev for persistent device permissions and naming)
4. Use SLES11 (with Powerpath and ASMLib)

do you have other suggestions? do you have comments on the pros and cons on this options.

Can someone from EMC or Oracle comment on the plans to make Powerpath available for OL6 with UEK2 ?

Regards,
Mihail
  • 1. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    Dude! Guru
    Currently Being Moderated
    Do you want to use ASMLib or Udev?
    Do you need Powerpath or can you use Multipath?

    Your frist milestone will be to answer Multipath or Powerpath.

    If Powerpath is your only option, then you are apparently limited to the RHEL kernel and have to use udev to set device ownerships.

    As far as I remember form previous similar posts, you can use Multipath instead of Powerpath for EMC Clariion. There are several examples available on the net, or ask EMC support about it.

    Once you are on Multipath, you are free to choose the kernel and ASMLib if you desire. In which case you'd choose the UEK kernel.

    The next question will be ASMLib or Udev. There are mixed opinions about it. If you are familiar with multipath and udev, you might might use it, or use ASMLib which is supposed to be easier to manage. ASMLib provides an alternative method to "o_direct" on block devices to avoid kernel buffering (I/O scheduler) under Linux. According to the developers, ASMLib provides an optimized direct I/O path for ASM and uses far less handles than the normal direct I/O path in the kernel.
  • 2. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    mdaskalov Newbie
    Currently Being Moderated
    Hi Dude,
    If I could answer this question only by my preference I would say I want Multipath (DM-MPIO).
    But as far as I could understand by reading http://www.emc.com/collateral/software/white-papers/h8180-powerpath-load-balancing-failover-wp.pdf (
    EMC PowerPath Load Balancing and Failover—Comparison with native MPIO operating system solutions) Powerpath have might significant perfermance benefits. (30% better when compared to Windows MPIO).
    Unfortunately I can't find any comparison with Linux 6 (RHEL6 and probably OL6) , and especially with the new load balancing algorithms ( service-time or queue-length ). Those new algorithms seem to me like they should ensure a very good performance in most situations (probablly somewhere near like Powerpath, if we assume Powerpath is the best).

    I would encourage anyone who can share his own opinion, or even better experience, to do it.

    So yes, the first question is: Powerpath, or Multipath?

    But how do we choose?
    I am not restricted by a policy, but I want the best performance possible, and the least problems combined.

    Regards,
    Mihail
  • 3. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    Dude! Guru
    Currently Being Moderated
    If the maximum load-balance performance is you goal than you need to go with EMC Powerpath, which has dedicated algorithms optimized for CLARiiON and Symmetrix arrays.

    Personally, I would reconsider though whether this theoretical advantage in case of port congestion is worth it to abandon the real benefits of Oracle Linux and UEK kernel and possible use of ASMLib.
  • 4. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    mdaskalov Newbie
    Currently Being Moderated
    Hi,
    I don't need maximum load balancing, I need maximum throughput and minimum latency of IO operations to the storage array. This configuration is going to be used for Oracle database, and I am looking for the best performance and stability configuration.

    I need some experience backed advice from real situation, so it would be good if you can share some numbers.

    I can see no benefits of Oracle Linux and UEK kernel if my disk IO have 30% less throughput, or 30% larger response time. Can you be more specific what you mean (by benefits).
  • 5. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    Dude! Guru
    Currently Being Moderated
    Powerpath and Multipath are device mappers that automate data path failover and recovery and use load balancing to optimize the use of available data paths. The performance you refer to is about IOPS when there is storage port congestion, comparing Windows round-robin with Powerpath load-balancing. It does not mean Powerpath will give you 30% more data throughput or 30% less I/O response time during standard operation.

    If you want to find out if there is a performance benefit using Powerpath instead of Multipath in your environment then I suggest to test it. It may take several hours to install and test the performance, but I'm afraid there is no other or better way to find out, or whether it is worth to replace the UEK kernel, which I doubt.

    By benefits I mean you cannot use ASMLib with the RHEL kernel of EL version 6 or later. For the other benefits:

    http://www.oracle.com/us/technologies/linux/uek-r2-features-and-benefits-1555063.pdf

    Btw, I just had a quick check in Google, pointing to the CLARiiON Support Forum and apparently Powerpath does support some versions of Oracle Linux: https://community.emc.com/message/565296. This message is somewhat old, I suggest you check what the current situation is at emc.com. The list of possible options you outlined in your initial post is probably not up to date.

    Edited by: Dude on Aug 17, 2012 1:49 PM
  • 6. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    mdaskalov Newbie
    Currently Being Moderated
    Hi Dude,
    unfortunately no references by EMC to UEK2 kernel on Oracle Linux 6.3.

    So far only UEK Kernel 2.6.32 is supported (for Oracle Linux 5.7 in Powerpath 5.6.0.2 (P02)).

    So as it seems currently the answer to my original question is No.

    Since Oracle stated they are working with partners on certification and hardware compatibility, I was hoping for someone to be able to say something.

    I was curious why there are not many validated configuration with OEL6.3, or OVM 3.1 (both with UEK2), and it seems that it's because there are no drivers yet for some of the standard 'Enterprise' components like EMC Powerpath.

    I can't test Powerpath v.s. dm-io without changing anything else...

    I could test "OEL6 with RHEL kernel + Powerpath" vs "OEL6 with UEK2 kernel + dm-mpio", but anyway this would not give the answer whether Powerpath is faster or slower than dm-mpio by itself, since the kernels would be different.

    Thanks, anyway for you help.
  • 7. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    Dude! Guru
    Currently Being Moderated
    I could test "OEL6 with RHEL kernel + Powerpath" vs "OEL6 with UEK2 kernel + dm-mpio", but anyway this would not give the answer whether Powerpath is faster or slower than dm-mpio by itself, since the kernels would be different.
    I wonder how the answer whether EMC Powerpath or DM Multipath is faster can help you? Apparently you cannot use Powerpath with the UEK2 kernel and have a certified system at the same time, at least not at this time. However there is no reason to throw the towel yet. If the use of Powerpath instead of Multipath is so critical, why not using Oracle Linux 5.7, which is certified? If you check the EMC compatibility matrix (esm_by_os), it actually shows some systems including Clariion supported for Oracle Linux 6.2 with UEK kernel. You might want to take a closer look.

    Anyway, it doesn't look like you will be able to solve the performance question without doing a real world test in your environment. You have no indication that Oracle Linux 6.3 with DM Mutlipath will give you less performance than RHEL 6.3 with Powerpath. Regarding the information you found, Linux is not Windows.

    Powerpath is not free and you have to pay a license, but worse, it will tie your system to a very specific version of the kernel. In case of RHEL 6 or later, it will deny you the use of Oracle specific products and features such as ASMLib, etc. Multipath seems to be the more economic and better solution since you do not have to worry about kernel versions and have the freedom to use whatever Oracle Linux has to offer.

    So, do you want to limit your kernel features and options and fix a problem that you don't know even know if it applies and pay money for it?

    Edited by: Dude on Aug 21, 2012 5:57 PM
  • 8. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    mdaskalov Newbie
    Currently Being Moderated
    Hi Dude,
    If the answer is that DM Multipath is faster than Powerpath, or even that DM Multipath is not slower than Powerpath in most conditions, than I would stop thinking about this.
    As I said I want (1st) the fastest possible performance with this hardware and (2nd) the least number of restrictions. The whole idea of the paper comparing the performance between powerpath and native multipathing (on Windows unfortunately) as I get it, was to show that powerpath is always optimal (as resulting performance) and native multipathing is worse (in some conditions the difference reaching 30%).
    It is kind of natural to have a feeling that "native multipathing" is similar on operating systems. So there are some "indications" that dm-mpio might be slower than powerpath, if powerpath was available on the specific operating system.

    Anyway, you are right that I could only answer this question about performance by doing some real test with different configurations.

    Thanks,
    Mihail
  • 9. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    Avi Miller Guru
    Currently Being Moderated
    mdaskalov wrote:
    It is kind of natural to have a feeling that "native multipathing" is similar on operating systems. So there are some "indications" that dm-mpio might be slower than powerpath, if powerpath was available on the specific operating system.
    This may be natural, but it's completely wrong: there is no similarity between the native multipathing on Windows and that on Linux, as they don't even share a common code base. So this assumption is invalid.

    You're also not considering the performance improvement when using ASMlib and it's optimized Direct I/O over the standard kernel I/O via PowerPath.

    Finally, EMC is currently working on PowerPath drivers for UEK2, so it (hopefully) shouldn't be too long before they're released. I'd probably run the UEK with ASMlib + PowerPath for now and then upgrade to UEK2+PowerPath when the drivers are released. Gives you the best of both possible worlds.
  • 10. Re: New Oracle Linux 6 installation - ASMLib and EMC Powerpath - is it possible
    mdaskalov Newbie
    Currently Being Moderated
    For any of you having the same trouble as I had, I am going to summarize my experience so far.

    Now (since dec 4) there is support from EMC in Powerpath 5.7SP1 for OEL6 U3 with UEK2. It turns out however, that the only supported kernels are 2.6.39-200* . Since we've already upgraded to 2.6.39-300* I couldn't install the module driver. I know I could have tried a few hacks, and eventually it would probably work, but I decided it is not worth the effort.

    We are currently running linux native multipath, and it seems to be good.

    Thanks everyone for helping out.

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