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CSE 598D Storage Systems, Spring 2007 Object Based Storage


CSE 598D Storage Systems, Spring 2007 Object Based Storage Presented By: Kanishk Jain Introduction Object Based Storage ANSI T10 Object-based Storage Devices Standard ... – PowerPoint PPT presentation

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Title: CSE 598D Storage Systems, Spring 2007 Object Based Storage

CSE 598D Storage Systems, Spring 2007Object
Based Storage
  • Presented By Kanishk Jain

  • Object Based Storage
  • ANSI T10 Object-based Storage Devices Standard
  • storage object a logical collection of bytes on
    a storage device, with well-known methods for
    access, attributes describing characteristics of
    the data, and security policies that prevent
    unauthorized access.
  • intelligent data layout

Object Storage Interface
  • OSD model is simply a rearrangement of existing
    data management functions
  • OSD is a level higher than block access but one
    level below file access

Background NAS sharing
  • NAS being used to share files among a number of
  • The files themselves may be stored on a fast SAN
  • The file server is used to intermediate all
    requests and thus becomes the bottleneck !

Background SAN sharing
  • The files themselves are stored on a fast SAN
    (e.g., iSCSI) to which the clients are also
  • While the file server is removed as a bottleneck,
    security is a concern !

Object-based storage security architecture
  • Metadata managers grant capabilities to clients
    clients present these capabilities to the devices
    on every I/O to ensure security
  • Secure separation of control and data path !

Development of OSD
  • Most initial work on object storage devices (OSD)
    was done at Parallel Data Lab at CMU
  • Focused on developing underlying concepts in two
    closely related areas NASD and Active Disks
  • Proposed as part of same project as NASD
  • Standardized by Storage Networking Industry
    Association (SNIA) in 2004.

OSD v/s Active Disks
  • OSD standard only talks about the interface.
  • It does not assume anything about the processing
    power at the disk.
  • OSD intelligence is software/firmware running at
    the disk (no specifications for this)
  • Processing power of an OSD can be scaled to meet
    the requirements of the functions an active disk

File System Application side (User Component
  • The OSD has the intelligence to perform basic
    data management functions such as space
    allocation, free space management etc., those
    functions are no longer part of the
    application-side file system.
  • Thus the application side file system is reduced
    to a manager an abstraction layer between user
    application and the OSD.
  • Only provides security and backward compatibility

File System - On the Device (Storage Component)
  • Workload offered to OSDs may be quite different
    from that of general-purpose file systems
  • At the OSD level, objects typically have no
    logical relationship, presenting a flat name
  • General-purpose file systems, which are usually
    optimized for workloads exhibiting relatively
    small variable-sized files, relatively small
    hierarchical directories, and some degree of
    locality are not effective in this case

Object based File System
  • Separation of metadata and data paths Separate
    metadata servers (MDS) manage the directory
    hierarchy, permissions and file to object
  • Distribution and replication of a file across a
    sequence of objects on many OSDs.
  • Example files systems Lustre, Panasas, Ceph

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Some Optimizations in Ceph
  • Partitioning the directory tree To efficiently
    balance load, the MDS partition the directory
    tree across the cluster. A client guesses which
    metadata server is responsible for a file, and
    contacts that server to open the file. That MDS
    will forward the request to the correct MDS if
    necessary. Distribution and replication of a file
    across a sequence of objects on many OSDs.
  • Limit on object size and use of regions Ceph
    limits objects to a maximum size (e. g., 1MB), so
    files are a sequence of bytes broken into chunks
    on the maximum object size boundary. Since only
    the MDS hold the directory tree, OSDs do not have
    directory information to suggest layout hints for
    file data. Instead, the OSDs organize objects
    into small and large object regions, using small
    block sizes (e. g., 4KB or 8KB) for small objects
    and large block sizes (e. g. 50100 of the
    maximum object size) for large objects.
  • Use of a specialized mapping algorithm A file
    handle returned by the metadata server describes
    which objects on which OSD contain the file data.
    A special algorithm, RUSH maps a sequence index
    to the OSD holding the object at that position in
    the sequence, distributing the objects in a
    uniform way.

Possible Performance Results
  • OBFS outperforms Linux Ext2 and Ext3 by a factor
    of two or three, and while OBFS is 1/25 the size
    of XFS, it provides only slightly lower read
    performance and 1040 higher write performance

Possible Performance Results (contd..)
Database Storage Management
  • Object attributes are also the key to giving
    storage devices an awareness of how objects are
    being accessed, so that it can use this
    information to optimize disk layout specific to
    the application.
  • Database software often has very little detailed
    information about the storage subsystem
  • Previous research took the view that a storage
    device can provide relevant characteristics to
  • Device-specific information is known to the
    storage subsystem, and thus it is better-equipped
    to manage low-level storage tasks

Database Storage Management (contd..)
  • Object attributes can contain information about
    the expected behavior of an object such as
    expected read/write ratio, access pattern
    (sequential vs. random), or expected size,
    dimension, and content of the object.
  • Using OSD, a DBMS can inform the storage
    subsystem of the geometry of a relation, thereby
    passing responsibility for low-level data layout
    to the storage device.
  • The dependency between the metadata and storage
    system/application is removed. This assists with
    data sharing between different storage

OSD Objects and Attributes
  • Scalability what does that word really mean
  • Capacity number of bytes, number of objects,
    number of files, etc. OSD aggregation techniques
    will allow for hierarchical representations of
    more complex objects that consist of larger
    numbers of smaller objects.
  • Performance Bandwidth, Transaction rate,
    Latency. OSD performance management can be used
    in conjunction with OSD aggregation techniques to
    more effectively scale each of these three
    performance metrics and maintain required QoS
    levels on a per-object basis.
  • Connectivity number of disks, hosts, arrays,
    etc. Since the OSD model requires self-managed
    devices and is transport agnostic the number of
    OSDs and hosts can grow to the size limits of the
    transport network.
  • Geographic LAN, SAN, WAN, etc. Again, since the
    OSD model is transport agnostic and since there
    is a security model built into the OSD
    architecture, the geographic scalability is not
  • Processing Power OSD processing power can be

Other Advantages
  • Manageability OSD management model relies on
    self-managed, policy driven storage devices, that
    can be centrally managed and locally administered
    (i.e. central policies, local execution).
  • Density OSD on individual storage devices can
    optimize densities by abstracting the physical
    characteristics of the underlying storage medium
  • Cost address issues such as /MB, /sqft,
    /IOP, /MB/sec, TCO, etc.
  • Adaptability to changing applications. Can the
    OSD be repurposed to different uses such as from
    a film editing station to mail serving?
  • Capability can add functionality for different
    applications. Can additional functionality be
    added to an OSD to increase its usefulness?

Other Advantages (contd..)
  • Availability Fail-over capabilities between
    cooperating OSD devices. 2-way failover versus
    N-way failover?
  • Reliability Connection-integrity capabilities
  • Serviceability Remote monitoring, remote
    servicing, hot-plug capability, genocidal
    sparing. When an OSD dies and a new one is put in
    its place, how does it get rebuilt? How
    automated is the service process?
  • Interoperability Supported by many OS vendors,
    file system vendors, storage vendors, middleware
  • Power decrease the power per unit volume by
    relying on the policy-driven self management
    schemes to power down objects (i.e. move them
    to disks and spin those disks down).

Cluster Computing
  • Traditionally 'divide-and-conquer' approach,
    decomposing the problem to be solved into
    thousands of independently executed tasks using a
    problem's inherent data parallelism--identifying
    the data partitions that comprise the individual
    task, then distributing each task and
    corresponding partition to the compute nodes for
  • Data from a shared storage system is staged
    (copied) to the compute nodes, processing is
    performed, and results are de-staged from the
    nodes back to shared storage when done. In many
    applications, the staging setup time can be
    appreciable-up to several hours for large

OSD for Cluster Computing
  • Object-based storage clustering is useful in
    unlocking the full potential of these Linux
    compute clusters.
  • Intrinsic ability to linearly scale in capacity
    and performance to meet the demands of the
    supercomputing applications.
  • High bandwidth parallel data access between
    thousands of Linux cluster nodes and a unified
    storage cluster over standard TCP/IP networks.

Commercial Products
OSD Commands
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