File Name: raid interview questions and answers .zip
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What is the most critical component in SAN? Each component has its own criticality with respect to business needs of a company. What is the need for separate network for storage why LAN cant be used? LAN hardware and operating systems are geared to user traffic, and LANs are tuned for a fast user response to messaging requests.
With a SAN, the storage units can be secured separately from the servers and totally apart from the user network enhancing storage access in data blocks bulk data transfers , advantageous for server less backups.
How many classes of service are available in Fibre Channel? What are the main constrains of SCSI in storage networking? What is a Fabric? A fabric is similar in concept to a segment in a local area network. Fibre Channel routing solution, and these bring substantial scalability benefits to the SAN architecture by allowing data to cross between different fabrics without merging them. What is RAID? Technology that groups several physical drives in a computer into an array that you can define as one or more logical drive.
Each logical drive appears to the operating system as single drive. This grouping enhances the performance of the logical drive beyond the physical capability of the drives.
What are the advantages of RAID? Redundant Array of Inexpensive Disks Depending on how we configure the array, we can have the 1. These can be used in combination to deliver the balance of performance and reliability that the user requires. Define RAID?
Which one you feel is good choice? Generally customer chooses R5 to achieve better redundancy and speed and it is cost effective. Provides improved performance and additional storage but no fault tolerance. Any disk failure destroys the array, which becomes more likely with more disks in the array. A single disk failure destroys the entire array because when data is written to a RAID 0 drive, the data is broken into fragments.
The number of fragments is dictated by the number of disks in the drive. The fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, giving this type of arrangement huge bandwidth. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the array means higher bandwidth, but greater risk of data loss R1 - Mirrored set without parity.
Provides fault tolerance from disk errors and failure of all but one of the drives. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing. Array continues to operate so long as at least one drive is functioning. Using RAID 1 with a separate controller for each disk is sometimes called duplexing. This mechanism provides an improved performance and fault tolerance similar to RAID 5, but with a dedicated parity disk rather than rotated parity stripes.
The single parity disk is a bottle-neck for writing since every write requires updating the parity data. One minor benefit is the dedicated parity disk allows the parity drive to fail and operation will continue without parity or performance penalty. R4 - Block level parity. Identical to RAID 3, but does block-level striping instead of byte-level striping. In this setup, files can be distributed between multiple disks.
The error detection is achieved through dedicated parity and is stored in a separate, single disk unit. R5 - Striped set with distributed parity. Distributed parity requires all drives but one to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure.
Upon drive failure, any subsequent. Storage Area Network Job Interview Questions reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive.
R6 - Striped set with dual distributed Parity. Provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical, especially for high availability systems. This becomes increasingly important because large-capacity drives lengthen the time needed to recover from the failure of a single drive. Single parity RAID levels are vulnerable to data loss until the failed drive is rebuilt: the larger the drive, the longer the rebuild will take.
Dual parity gives time to rebuild the array without the data being at risk if one drive, but no more, fails before the rebuild is complete. Explain different types of RAID? RAID 0: data striping blocks are written sequentially, no redundancy, high performance than single disk access. Read can be distributed across both the disks to increase performance. RAID 3: Striping with byte parity, adds parity information to rebuild data in the event of disk failure, high transfer rate and availability with lower capacity required than RAID 1.
Transactions performance low because all disks operate in lock step. RAID 4: striping with block parity, independently accessible disks, data blocks written sequentially to each disk failure. Dedicated parity disk is write bottleneck and leads to poor performance.
RAID 5: Striping with rotational parity, parity blocks written per row and distributed across all disks, parity distribution eliminates single write bottleneck overhead for parity calculation on write supplemented with parallel microprocessors or caching. The array continues to operate with one or more drives failed in the same mirror set, but if drives fail on both sides of the mirror the data on the RAID system is lost.
In this RAID level if one disk is failed full mirror is marked as inactive and data is saved only one stripped volume. The array can sustain multiple drive losses so long as no mirror loses both its drives. What are the types of disk array used in SAN? What is Array? Probability of unavailability of data stored on the disk array due to single point failure is totally eliminated. Set of high performance storage disks that can store several terabytes of data.
Single disk array can support multiple points of connection to the network. You need to have at least 3 disk drives to create R5. Can you name some of the states of RAID array? No, since R0 is not redundant array, failure of any disks results in failure of the entire array so we cannot rebuild the hot spare for the R0 array.
What is zoning? Fabric management service that can be used to create logical subsets of devices within a SAN. This enables portioning of resources for management and access control purpose. What are the two major classification of zoning? Two types of zoning are: a Software Zoning.
What are different levels of zoning? What is virtualization? A technique of hiding the physical characteristics of computer resources from the way in which other system application or end user interact with those resources. Aggregation, spanning or concatenation of the combined multiple resources into larger resource pools. What is storage virtualization?
What is LUN Masking? A method used to create an exclusive storage area and access control. And this can be achieved by storage device control program.
What are two types of recording techniques on the tapes? Name few types of Tape storage? What is snapshot? A snapshot of data object contains an image of data at a particular point of time. What is stripe-unit-size? It is data distribution scheme that complement s the way operating system request data. Granularity at which data is stored on one drive of the array before subsequent data is stored on the next drive of the array.
What is hot-swapping? Devices are allowed to be removed and inserted into a system without turning off the system. What is Hot-Sparing? A spare device is available to be inserted into the subsystem operation without having to remove and replace a device. What is HSM? Hierarchical Storage Management - An application that attempts to match the priority of data with the cost of storage. What are different types of backup system? What is bad block reallocation? A bad sector is remapped or reallocated to good spare block and this information is stored in the internal table on the hard disk drive.
Apart from the new generation of HDD comes with a technology called BGMS background media scan which continuously scans the HDD media for defects and maps them when the drive is idle this is performed after the HDD is attached to the system.
Earlier it is used to be very costly to buy even a smaller size of disk, but nowadays we can buy a large size of disk with the same amount like before. Raid is just a collection of disks in a pool to become a logical volume. Raid contains groups or sets or Arrays. It can be a minimum of 2 number of disk connected to a raid controller and make a logical volume or more drives can be in a group. Only one Raid level can be applied in a group of disks.
Fast redeployment, by unplug and plug, of an existing database to a new platform. Triggers, tables, procedures, views, keys etc are typical examples. When a table or view is dropped, any views in the same database are also dropped. Here Mindmajix shares top real-time Teradata questions. The logical components are usually used to connect to the database. These are scenario-based questions that test the depth of your knowledge. Answer: Database is an organized collection of related data where the data is stored and organized to serve some specific purpose.
Question 1. What Is Raid? Answer: Redundant Array of Independent Drives (or Disks), also known as Redundant Array of Inexpensive Drives .
A large number of disks in a system improves the rate at which data can be read or written :. If the mean time to failure of a single disk is , hours, then the mean time to failure of some disk in an array of disks will be :. The mean time to failure of a mirrored disk depends on : I the mean time to failure of individual disks II the mean time to repair. They are explained in elaborated manner to get clear subject knowledge.
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Post a comment. It is the Stripped Disk Array with no fault tolerance and it requires at least 2 drives. To be implemented. Due to no redundancy feature, RAID 0 is considered to be the.
We have 0 through 5 RAID levels that offers different levels of performance and fault tolerance. What is RAID controller technology?
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What is the most critical component in SAN?