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Sun ZFS 7120 Storage for RAC as ASM

Discussion in 'Installation - Unix and Unix Like' started by prashant, Jul 29, 2011.

  1. prashant

    prashant Forum Advisor

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    Hi,

    We are planning to use Sun ZFS 7120 storage for our RAC system(with ASM).

    Has anyone used this storage as ASM?

    Also, could some share advantages/disadvantages of a NAS storage over SAN storage.

    Best Regards,
    Prashant

    Platform : Solaris Sun Sparc (64-bit)
    DB : Oracle 10.2.0.4 Standard Edition
     
  2. prashant

    prashant Forum Advisor

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    Following information gives a good insight for NAS storage used for ASM based File System in Oracle Real Application Clusters:-


    NAS Concept:

    a) Network attached storage and NAS devices are a specialized file servers optimized for serving storage, using TCP/IP over a local area network (LAN).

    b) NAS devices provide file I/O access, whereas SAN and DAS architectures provide block I/O storage access.

    c) NAS file I/O (file open/close, read/write) is redirected over the network. Thus the block-to-file I/O abstraction layer takes place in the NAS device instead of the host.

    d) NAS devices and NAS I/O traffic run across the LAN, which could impact the enterprise LAN environment.



    For this reason, it is recommended to configure NAS traffic on a segmented network, isolated from the public network traffic.


    Limitations of NAS:


    a) It can experience high network traffic loads on the LAN and thus is limited by LAN bandwidth.

    b) The NAS device itself can be a bottleneck.

    c) I/O performance is still limited by file I/O access that is, it is not block I/O.


    SAN Vs NAS:

    a) SANs provide I/O access to hosts, whereas NAS appliances provide file level I/O.

    b) SANs also differ from other storage architectures in that they are dedicated storage networks and use their own network protocols (FC) and hardware components.

    c) Unlike NAS, SAN I/O traffic does not impact IP (LAN) traffic.

    d) SANs are the best way to ensure predictable performance and constant data availability and reliability.


    ASM:

    ASM is like any other volume manager in that the client (eg RDBMS ), not the volume manager, determines the size of the I/O.

    If the RDBMS makes a request that spans multiple disks, then ASM issues multiple requests, but it cannot do an I/O that is larger than the client's buffer.



    Although customers who deploy ASM typically use FC or Internet small computer interface (iSCSI) devices, ASM can also leverage NFS-based files as ASM disks.

    However, this is NOT considered to be the most optimal architecture because of the several filesystem layers involved for example, ASM (which is a filesystem) over NFS over the internal filesystem).

    Additionally, because NFS-based storage and ASM provides some overlapping functionality, it is difficult to deploy ASM over NFS without reducing the benefit of either component's core features.



    Nevertheless, there are circumstances where ASM on NFS is applicable, such as when you need to provide uniformity of operating procedures or to satisfy product, host OS, and/or other environmental constraints.



    One must decide which solution is most appropriate for your environment (NAS or SAN) based on your business requirements.


    Best Regards,
    Prashant
     
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