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Basic storge system terms required to consult a solution

  • Sep 25 / 2008
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DBA Interview questions, dbDigger, Storage

Basic storge system terms required to consult a solution

Before you sit down with a storage administrator or engineer to map out your plans for disk configuration, here are basic preparation steps to take. Start by getting familiar with the terms below and communicate your requirements much easier.

  • RAID – Redundant Array of Inexpensive Disks, also known as Redundant Array of Independent Disks.

  • Disk subsystem – A general term that refers to the disks on the server.

  • Spindle – Spindles are another way to refer to the physical disk drives that make up the RAID array.

  • I/O Ops – Input/Output operations, usually measured per second.

  • Queuing – Number of I/O Ops that are pending completion by the disk subsystem.

  • SAN – Storage area networks are collections of storage devices and fibre switches connected together along with the servers that access the storage on the device. SAN has also become a generic term, which refers to the physical storage drives such as EMC, 3PAR and Hitachi.

  • LUN – Logical Unit Number – This is the identification number assigned to a volume when created on a SAN device.

  • Physical drive – How Windows sees any RAID array, single drive or LUN that is attached to the server.

  • Logical drive – How Windows presents drives to the user (C:, D:, E:, etc.).

  • Block size – The amount of data read from the spindles in a single read operation. This size varies per vendor from 8 KB to 256 MB.

  • Hardware array – A RAID array created using a physical RAID controller.

  • Software array – A RAID array created within Windows using the computer management snap-in.

  • Hot spare – A spindle that sits in the drive cage and is added to the array automatically in the event of a drive failure. While this does not increase capacity, it does reduce the amount of time that the array is susceptible to data loss because of a second failed drive.

  • Recovery time – Amount of time needed for the RAID array to become fully redundant after a failed drive has been replaced, either manually or automatically via a hot spare.

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