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  • Automatic Storage Management

    UKOUG RAC & HA SIGSeptember 30, 2010

    Frits Hoogland

    1

  • Poll Anyone using ASM currently?

    Version of ASM?10.110.211.111.2

    Anyone using OMF?As part of ASM implementationWithout ASM?

    2

  • ASM - The Oracle definitonhttp://www.oracle.com/technology/products/database/asm/index.html:

    (link now gone)

    Automatic Storage Management (ASM) is a feature in Oracle Database 10g/11g that provides the database administrator with a simple storage management interface that is consistent across all server and storage platforms. As a vertically integrated file system and volume manager, purpose-built for Oracle database files, ASM provides the performance of async I/O with the easy management of a file system. ASM provides capability that saves the DBAs time and provides flexibility to manage a dynamic database environment with increased efficiency.

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    http://www.oracle.com/technology/products/database/asm/index.htmlhttp://www.oracle.com/technology/products/database/asm/index.html

  • ASM - The Oracle definiton Storage management interface that is

    consistent across all server and storage platforms

    Vertically integrated file system and volume manager

    Purpose-built for Oracle database files Performance of async I/O with the easy

    management of a filesystem(http://www.oracle.com/technology/products/manageability/database/pdf/asmov.pdf)

    4

    http://www.oracle.com/technology/products/manageability/database/pdf/asmov.pdfhttp://www.oracle.com/technology/products/manageability/database/pdf/asmov.pdf

  • The database and ASM ASM components

    (s)pfileCSS

    The function of the ASM instanceDisk and diskgroup managementDatabase and ASM disk I/O

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  • Redundancy Volume manager capabilities

    External redundancyNo redundancy at ASM level

    Normal redundancyMirroring at ASM level

    High redundancyTriple mirroring at ASM level

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  • Redundancy Is your storage redundant?

    Purpose of redundancy: stretch MTBF

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  • ASM terminology ASM instance Diskgroup Disk Failgroup AU (allocation unit)

    8

  • AU Spreading

    9

    AU 10-

    AU 0-

    AU 50-

    AU 40-

    AU 30-

    AU 20-

    Disk header (name, AT, FST, PST)

    File directory

    Disk directory

    Active Change Directory

    Continuing Operation Directory

    Template Directory

    Alias Directory

    Free AU

    Disk1

  • AU Spreading

    10

    AU 10-

    AU 0-

    AU 50-

    AU 40-

    AU 30-

    AU 20-

    Disk header (name, AT, FST, PST)

    File directory

    Disk directory

    Active Change Directory

    Continuing Operation Directory

    Template Directory

    Alias Directory

    Free AU

    Disk1 Disk2

  • AU Spreading

    11

    AU 10-

    AU 0-

    AU 50-

    AU 40-

    AU 30-

    AU 20-

    Disk header (name, AT, FST, PST)

    File directory

    Disk directory

    Active Change Directory

    Continuing Operation Directory

    Template Directory

    Alias Directory

    Free AU

    Disk1 Disk2 Disk3

  • Allocation policiesScenario 1:

    Allocation of 10 AUsDiskgroup DG1; 1 disk: D1

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    DG1,D1 0 ... 50 51 52 53 54 55 56 57 58 59 60

  • Allocation policiesScenario 2: Allocation of 10 AUs Diskgroup DG1; 2 disks: D1,D2 (equally sized)

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    DG1,D1 0 ... 50 51

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    52

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    30DG1,D2 0 ... 25

  • Allocation policiesScenario 3:

    Allocation of 10 AUsDiskgroup DG1; normal redundacy2 FGs: FG1,FG2; 4 disks: D1,D2,D3,D4 (eq. sized)

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    DG1,FG1,D1 0 ... 50

    DG1,FG1,D2 0 ... 25

    DG1,FG2,D3

    DG1,FG2,D4

    0 ... 50

    0 ... 25

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    51

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  • Scenario 4: Allocation of AUsDiskgroup DG1; external redundacy3 disks: D1,D2,D3 (eq. sized)

    Allocation policies

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    DG1,D1 0 ... 50

    DG1,D2 0 ... 25

    DG1,D3 0 ... 17

    51

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    3026

    52

    27

    53

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    55

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    ORA-15041: diskgroup space exhausted

  • Scenario 5: Allocation of 10 AUsDiskgroup DG1; external redundacy2 disks: D1,D2 (unequally sized)

    Allocation policies

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    DG1,D1 0 ... 50

    DG1,D2 0 ... 25

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    26 27

    52

    28 29

    53

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  • How ASM tunes I/O I/O tuning is done using the allocation policy

    This means no tuning is done on runtime

    Mirror/secondary AU readsASM_PREFERRED_READ_FAILURE_GROUPCorruption found

    Unequal sized disk (!!)

    17

  • Oracle Managed Files First appeard in version 9 Goal: easy database files management Did never gain wide acceptance (AFAIK)

    Re-introduced with ASM

    18

  • Oracle Managed Files OMF & ASM are separate options

    OMF can be used without ASM, and vice versa

    OMF makes sense with ASMFile structure standardisationFile naming standardisationNo manual action needed with file manipulationDatabase removal?

    19

  • ASM Disks ASM sees a disk as an individual entity

    That is why ASM stripes everything over all disks

    Is a disk a real individual entity nowadays?SAN/NAS anyone?Anyone who uses DAS for production databases?

    20

  • ASMLib Support library for ASM

    Kernel module

    Disks for ASM can be used in three ways:Raw devicesBlock devicesASMLib devices

    21

  • ASMLib Rumored to have started as a framework for

    storage vendors to add functionality

    Reported functionality:Device name labelsDevice ownership and permissionsAsync I/O management I/O optimisationSanity checkups

    - (http://blogs.oracle.com/AlejandroVargas/newsItems/viewFullItems$96)

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  • ASMLib Device name labels

    NOT the diskname in ASM

    Device ownership and rightsASMLib creates a meta device with correct rightsClusterware filesCan be accomplished with udev

    - (http://www.oracle.com/technology/products/database/asm/pdf/device-mapper-udev-crs-asm%20rh4.pdf)

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    http://www.oracle.com/technology/products/database/asm/pdf/device-mapper-udev-crs-asm%20rh4.pdfhttp://www.oracle.com/technology/products/database/asm/pdf/device-mapper-udev-crs-asm%20rh4.pdf

  • ASMLib Async I/O management

    Using ASMLib theres a synchronous write to meta-device

    Async I/O is enabled by default

    I/O optimisationSame I/O using different codepathNo I/O optimisation in ASMLib according to Wim Coekaerts- (http://forums.oracle.com/forums/thread.jspa?threadID=498215)

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    http://forums.oracle.com/forums/thread.jspa?threadID=498215http://forums.oracle.com/forums/thread.jspa?threadID=498215

  • ASMLib Sanity checkups

    Ownership and rights?Can anyone think of any other checkup?

    Partition/disk name persistence/dev/sd*/dev/disk/by-id/ !ASM recognises disks by name in the diskheader!

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  • ASMLib Do NOT use ASMLib

    No added functionality which can not be resolved in an other way

    Extra layer in the technology stackAdd a kernel dependencyOnly available on linux

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  • Advantages of ASM (Part of) volume manager- & filesystem-

    management become DBA responsibility Database files become black boxed Everything always striped over all disks in a

    diskgroup RMAN mandatory for backup & restore No filesystem imposed limits RAC / cluster aware

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  • Disadvantages of ASM (Part of) volume manager- & filesystem-

    management becomes DBA responsibility Database files become black boxed Everything always striped over all disks in a

    diskgroup RMAN mandatory for backup & restore Relative young Unequal disk sizes give unequal I/O

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  • Conclusion File / filesystem management

    Error proneHard to maintain standards

    Principal deployment of SAMEWhich is goodNecessary to know ASM inner working

    Rebalancing ASM and online storage migration

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  • Q & A

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  • Bibliography http://docs.oracle.com http://otn.oracle.com http://dims.ncsa.uiuc.edu/san/src/linux-

    mpio.pdf http://jarniel.wordpress.com http://canali.web.cern.ch/canali

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    http://docs.oracle.comhttp://docs.oracle.comhttp://otn.oracle.comhttp://otn.oracle.comhttp://dims.ncsa.uiuc.edu/san/src/linux-mpio.pdfhttp://dims.ncsa.uiuc.edu/san/src/linux-mpio.pdfhttp://dims.ncsa.uiuc.edu/san/src/linux-mpio.pdfhttp://dims.ncsa.uiuc.edu/san/src/linux-mpio.pdfhttp://jarniel.wordpress.comhttp://jarniel.wordpress.comhttp://canali/web.cern.ch/canalihttp://canali/web.cern.ch/canali