What is Oracle ASM?
The Oracle® automatic storage management system (ASM) was developed 10 years ago to make it much easier for database administrators (DBAs) to use and tune database storage. Oracle ASM enables DBAs to:

  • Automatically stripe data over each RAW device to improve database storage performance
  • Mirror data for greater fault tolerance
  • Simplify the management and extension of database storage for the cloud and, with the ASM Cluster File System (ACFS), use the snapshot and replication functionality to increase availability
  • Add the Oracle Real Application Clusters (RAC) capability to help reduce total cost of ownership (TCO), expand scalability and increase availability, among other benefits
  • Easily move data from one device to another while the database is active with no performance degradation
  • Reduce or eliminate storage or Linux administrator time for configuring database storage
  • Use ASM as a Linux®/Unix operating system file system called ACFS. (I know what you are thinking. Since you need Oracle Grid up and running to mount and use ASM, how can an ACFS device be available to the operating system at system boot? The reason is that the kernel has been modified to allow this functionality. Learn more about ACFS here.)
  • What’s more, it’s free – comes with Oracle Grid

The drawbacks of using Oracle ASM:

  • DBAs now control the storage they are using. Therefore, they need to know more about the storage and how the logical unit numbers (LUNs) are being used by Oracle ASM, and how to create ASM disk groups for higher performance.
  • Most ASM commands are executed through SQLPlus, not through the command line. That means storage is accessed through SQLPlus and sometimes ASMCMD, isolating the storage and making it harder for Linux admins to identify storage issues.
  • Recover Manager (RMAN) is the only guaranteed/supported method of backing up databases on ASM.

What will be covered in this blog and what won’t
ASM is quite complex to learn and to set up properly for both performance and high availability. I won’t be going over all the commands and configurations of ASM, but I will cover how to set up an aligned LSI Nytro WarpDrive and Nytro MegaRAID PCIe® card and create an ASM disk to be assigned to an ASM disk group. There are many websites and books that go over all the details of Oracle ASM, and the most current book that I would recommend is “Database Cloud Storage: The Essential Guide to Oracle Automatic Storage Management.” Or visit Oracle’s docs.oracle.com website.

Setting up ASM
The following steps cover configuring a LUN for ASM. In order to use ASM, you will need to install the Oracle Grid software from otn.oracle.com. I prefer using Oracle ASMLIB when configuring ASM.  Included in the box of the latest version of Oracle Linux,  ASMLIB offers an easier way to configure ASM. If you are using an older version of ASM, you will need to install the RPMs for ASM from support.oracle.com.

Step 1: Create aligned partition
Refer to Part 1 of this series to create a LUN on a 1M boundary. Oracle recommends using the full disk for ASM, so just create one large aligned partition. I suggest using this command:

echo “2048,,” | sfdisk –uS /dev/sdX –force

Step 2: Create an ASM disk
Once the device has an aligned partition created on it, we can assign it to ASM by using the ASM createdisk command with two input parameters – ASM disk name and the PCIe flash partitioned device name – as follows:

/etc/init.d/oracleasm createdisk ASMDISK1 /dev/sda1

To verify that the create ASM disk process was successful, and the device was marked as an ASM disk, enter the following commands:

/etc/init.d/oracleasm querydisk /dev/sda1

(the output should state: “/dev/sda is an Oracle ASM disk [OK])

/etc/init.d/oracleasm listdisks

(the output should state: ASMDISK1)

Step 3: Assign ASM disk to disk group
The ASM disk group is the primary component of ASM as well as the highest level data structure in ASM. A disk group is a container of multiple ASM disks, and it is the disk group that the database references when creating Oracle Tablespaces.

There are multiple ways to create an ASM disk group. The easiest way is to use ASM Configuration Assistant (ASMCA), which walks you through the creation process. See Oracle ASM documentation on how to use ASMCA.

Here are the steps for creating a disk group:

a: Log in to GRID using sqlplus / as sysasm.

b: Select name, path, header status, state from v$asm_disk as follows:

c: Create diskgroup DG1 external redundancy disk using this command:

‘/dev/oracleasm/disks/D1’;

The disk group is now ready to be used in creating an Oracle database Tablespace. To use this disk group in an Oracle database, please refer to Oracle’s database documentation at docs.oracle.com.

In Part 4, the final installment of this series, I’ll discuss how to persist assignment to dynamically changing  Nytro WarpDrive and Nytro MegaRAID PCIe cards.

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How did he do that?
Growing up, I watched a little TV.  Okay, a lot of TV as I did not have my DVR or iPad and a man who would one day occupy the White House as VP had not yet invented the Internet.  Of the many shows I watched, MacGyver was one of my favorites. He would take ordinary objects and use them to solve complicated problems in a way no one could have imagined. Out of all the things he used, his trusty Swiss army knife was the most awesome.  With all its blades, tools and accessories, it could solve multiple problems at the same time.  It was easy to use, did not take up a lot of space and was very cost-effective.

Nytro MegaRAID – the Swiss Army knife of server storage
LSI has its own multi-function, get-yourself-out-of-a-fix workhorse – the Nytro MegaRAID® card, part of the Nytro product family. It combines caching intelligence, RAID protection and flash on a single PCIe® card to accelerate applications, so it can be deployed to solve problems across a broad number of applications.

A feature for every challenge!
The Nytro MegaRAID card is built on the same trusted technology as the MegaRAID cards deployed in datacenters worldwide. That means, it is enterprise architected and hardened and datacenter tested.  Its Swiss Army knife-like features include, as I mentioned, on-board flash storage that can be configured to monitor the flow of data from an application to the attached RAID protected storage, intelligently identify hot, or the most frequently accessed, data, and automatically move a copy of that data to the flash storage to accelerate applications.   The next time the application needs that data, the information is fetched from flash, not the much slower traditional hard disk drive (HDD) storage.

Hard drives can lead to slowdowns in another way, too, when the mechanics wear out and fail. When they do, your storage (and application) performance can dramatically decrease – in a RAID storage environment, this is called degraded mode. The good news is that the Nytro MegaRAID card stores much of an application’s frequently used data in its intelligent flash based cache, boosting the performance of a connected HDD in degrade mode by as much as 10x, depending on the configuration.  The Swiss Army knife follow-on benefit is that when you replace the failed drive, Nytro MegaRAID speeds RAID storage rebuilds by as much as 4x.  RAID rebuilds add to IT admin time, and IT time is money, so that’s money you get to keep in your pocket.

The Nytro MegaRAID card also can be configured so you can use half of its onboard flash as a pair of mirrored boot drives.  In big data environments, this mirroring frees up two boot drives for use as data storage to help increase your server storage density (aka available storage capacity), often significantly, while dramatically improving boot time.  What’s more, that same flash can be deployed instead as primary storage to complement your secondary HDD storage with higher speeds, providing a superfast repository for key files like virtual desktop infrastructure (VDI) golden images or key database log files.

One MacGyver Swiss Army knife, one Nytro MegaRAID card – both easy-to-use solutions for a number of complex problems.

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