Comparation between ASM note [ID 373242.1] and note [ID 452924.1]

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4 responses to “Comparation between ASM note [ID 373242.1] and note [ID 452924.1]”

1. 

   admin

   April 29, 2011

   Lun Size And Performance Impact With Asm

   QUESTION

   What is the maximum LUN size we can use without performance degradation? For example, is 1 TB or 2TB sized LUNs perform the same as 100 GB or 200 GB sized LUNs?

   We are using the ASM feature of Oracle DB 10g release 2 on 64-bit Solaris 9 or Solaris 10.

   Solution

   ANSWER

   Size alone should not affect the performance of a LUN. The underlying hardware is what counts. There is no magic number for the LUN size. Seek the advice of the storage vendor to recommend the best configuration from a raid 1 or 5 perspective for performance and availability since this may vary between vendors. Given a database size and storage hardware you have available, our best practice recommends creating larger LUNs (if possible to reduce LUN management for the sys admins) and create LUNs from separate set of storage arrays (drives) so that LUNs are not sharing drives if possible.

   For larger LUNs it is recommended using a large ALLOCATION UNIT.

   Reply
2. 

   admin

   April 29, 2011

   How to Prepare Storage for ASM

   Applies to:
   Oracle Server – Enterprise Edition – Version: 10.1.0.2 to 11.2.0.2.0 – Release: 10.1 to 11.2
   Information in this document applies to any platform.
   Oracle Server Enterprise Edition – Version: 10.1.0.2 to 11.2.0.2

   ***Checked for relevance on 03-Dec-2010***
   Goal
   This document describes how to prepare your storage sub-system before you configure Automatic Storage Management (ASM). When preparing your storage to use ASM, first determine the storage option for your system and then prepare the disk storage for the specific operating system environment.
   Solution

   A) You can create an ASM diskgroup using one of the following storage resources:

   1) Raw disk partition—A raw partition can be the entire disk drive or a section of a disk drive.
   However, the ASM disk cannot be in a partition that includes the partition table because the
   partition table can be overwritten.

   2) Logical unit numbers (LUNs)—Using hardware RAID functionality to create LUNs is a recommended
   approach. Storage hardware RAID 0+1 or RAID5, and other RAID configurations, can be provided to
   ASM as ASM disks.

   3) Raw logical volumes (LVM)—LVMs are supported in less complicated configurations where an LVM
   is mapped to a LUN, or an LVM uses disks or raw partitions. LVM configurations are not recommended
   by Oracle because they create a duplication of functionality. Oracle also does not recommended
   using LVMs for mirroring because ASM already provides mirroring.

   4) NFS files—NFS files are suitable for testing, but are not a recommended configuration for production environments. Using NFS files with ASM duplicates ASM functionality. Though, NetApp as an NFS vendor certifies its product with ASM. So there are customers using NFS and ASM together.

   B) The procedures for preparing storage resources for ASM are:

   1) Identify or create the storage devices for ASM by identifying all of the storage resource
   device names that you can use to create an ASM disk group. For example, on Linux systems, device
   names are typically presented from the /dev directory with the /dev/device_name_identifier name
   syntax.

   2) Change the ownership and the permissions on storage device resources. For example, the
   following steps are required on Linux systems:

   2.1) Change the user and group ownership of devices to oracle:dba
   2.2) Change the device permissions to read/write
   2.3) On older Linux versions, you must configure raw device binding

   After you have configured ASM, ensure that disk discovery has been configured correctly by setting
   the ASM_DISKSTRING initialization parameter.

   Note: Setting the ownership to oracle:dba is just one example that corresponds to the default
   settings. A non-default installation may require different settings. In general, the owner of the
   disk devices should be the same as the owner of the Oracle binary. The group ownership should be
   OSDBA of the ASM instance, which is defined at installation.

   C) Recommendations for Storage Preparation. The following are guidelines for preparing storage for
   use with ASM:

   1) Configure two disk groups, one for the datafile and the other for the Flash Recovery Area. For
   availability purposes, one is used as a backup for the other.

   2) Ensure that LUNs, which are disk drives of partitions, that ASM disk groups use have similar
   storage performance and availability characteristics. In storage configurations with mixed speed
   drives, such as 10K and 15K RPM, I/O distribution is constrained by the slowest speed drive.

   3) Be aware that ASM data distribution policy is capacity-based. LUNs provided to ASM have the
   same capacity for each disk group to avoid an imbalance.

   4) Use the storage array hardware RAID 1 mirroring protection when possible to reduce the
   mirroring overhead on the server. Use ASM mirroring redundancy in the absence of a hardware RAID,
   or when you need host-based volume management functionality, such as mirroring across storage
   systems. You can use ASM mirroring in configurations when mirroring between
   geographically-separated sites over a storage interface.

   Hardware RAID 1 in some lower-cost storage products is inefficient and degrades the performance of
   the array. ASM redundancy delivers improved performance in lower-cost storage products.

   5) Maximize the number of disks in a disk group for maximum data distribution and higher I/O
   bandwidth.

   6) Create LUNs using the outside half of disk drives for higher performance. If possible, use
   small disks with the highest RPM.

   7) Create large LUNs to reduce LUN management overhead.

   8) Minimize I/O contention between ASM disks and other applications by dedicating disks to ASM
   disk groups for those disks that are not shared with other applications.

   9) Choose a hardware RAID stripe size that is a power of 2 and less than or equal to the size of
   the ASM allocation unit.

   10) Avoid using a Logical Volume Manager (LVM) because an LVM would be redundant. However, thereare situations where certain multipathing or third party cluster solutions require an LVM. In
   these situations, use the LVM to represent a single LUN without striping or mirroring to minimize
   the performance impact.

   11) For Linux, when possible, use the Oracle ASMLIB feature to address device naming and
   permission persistency.

   12) ASMLIB provides an alternative interface for the ASM-enabled kernel to discover and access
   block devices. ASMLIB provides storage and operating system vendors the opportunity to supply
   extended storage-related features. These features provide benefits such as improved performance
   and greater data integrity.

   Reply
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