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EMC interview Questions and Answers

What Is Lun Masking?

LUN (Logical Unit Number) Masking is an authorization process that makes a LUN available to some hosts and unavailable to other hosts.

LUN Masking is implemented primarily at the HBA (Host Bus Adapter) level. LUN Masking implemented at this level is vulnerable to any attack that compromises the HBA. Some storage controllers also support LUN Masking.

Why We Need Lun Masking?

LUN Masking is important because Windows based servers attempt to write volume labels to all available LUN’s. This can render the LUN’s unusable by other operating systems and can result in data loss.

Device masking lets you control your host HBA access to certain storage arrays devices. A device masking database, based in the storage arrays unit, eliminates conflicts through centralized monitoring and access records. Both HBA and storage arrays director ports in their Channel topology are uniquely identified by a 64-bit World Wide Name (WWN). For ease of use, you can associate an ASCII World Wide Name (AWWN) with each WWN.

How Will You Ensure That San-attached Tape Devices Are Represented Consistently In A Host Operating System?

  • Use the Persistent Binding for Tape Devices.
  • Persistent binding is a host-centric enforced way of directing an operating system to assign certain SCSI target IDs and LUNs.
  • Persistent Name Binding support is for target devices.
  • Persistent binding is provided for users to associate a specified device World Wide Port Name (WWPN) to a specified SCSI target ID.
  • For example, where a specific host will always assign SCSI ID 3 to the first router it finds, and LUNs 0, 1, and 2 to the three-tape drives attached to the router.

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What Is Lun, Logical Unit Number?

Logical Unit Number or LUN is a logical reference to entire physical disk, or a subset of a larger physical disk or disk volume or portion of a storage subsystem.

What Is Wwn Zoning?

WWN zoning uses name servers in the switches to either allow or block access to particular World Wide Names (WWNs) in the fabric. A major advantage of WWN zoning is the ability to recable the fabric without having to redo the zone information. WWN zoning is susceptible to unauthorized access, as the zone can be bypassed if an attacker is able to spoof the World Wide Name of an authorized HBA.

What’s Port Zoning?

Port sectionalisation utilizes physical ports to outline security zones. A user’s access to knowledge is decided by what physical port he or she is connected to. With port sectionalisation, zone info should be updated whenever a user changes switch ports. additionally, port sectionalisation doesn’t enable zones to overlap. Port sectionalisation is generally enforced victimization onerous sectionalisation, however might even be enforced victimization soft sectionalisation.

What’s The distinction Between onerous And Soft Zoning?

Hard sectionalisation is sectionalisation that is enforced in hardware.

Soft sectionalisation is sectionalisation that is enforced in code.

Hard sectionalisation physically blocks access to a zone from any device outside of the zone.

Soft sectionalisation uses filtering enforced in fibre channel switches to forestall ports from being seen from outside of their assigned  zones. the protection vulnerability in soft sectionalisation is that the ports are still accessible if the user in another zone properly guesses the fibre channel address.

Justify The Device Masking design In Storage Arrays?

The device masking commands enable you to:

Assign and mask access privileges of hosts and adapters

Connected in an exceedingly Fibre Channel topology to storage arrays and devices.

Specify the host bus adapters (HBAs) through that a bunch will access storage arrays devices.

Display or list device masking objects and their relationships: Typical objects ar hosts, HBAs, s     storage arrays devices, and Fibre Channel Adapter (FA) ports.

Modify properties, like names and access privileges related to device masking objects (for example, modification the Name of a host).

However, does one grasp What sort of Fibre Cable Is Needed?

Select it on the idea of transmission distance.

If the space is a smaller amount than some of miles, i will be able to use multimode fibre cable.

If the space is quite 3-5 miles, i will be able to use single mode fibre cable.

However, can You Calculate Raw Capacity?

Raw Capacity= Usable + Parity

However, can You Calculate the specified Band breadth With Write Operations?

The needed Bandwidth=the required information measure is decided by mensuration the common range of write operations and therefore the average size of write operations over a amount of your time.

A way to Calculate Rpms Of Ssd?

SSD drives haven’t any movable elements and so haven’t any rev.

However, can You Calculate Iops Per Drive?

To calculate IOPS per drive the formula I will use is:

1000 / (Seek Time + Latency) = IOPS

Are you able to allot A Lun Larger Than two.19tb Limit Of Mbr ?

Use GPT.

GUID Partition Table, GPT may be a a part of the EFI normal that defines the layout of the partition table on a tough drive. GPT provides redundancy by writing the GPT header and partition table at the start of the disk and additionally at the tip of the disk.

GPT Uses 64-bit LBA for storing Sector numbers. GPT disk will in theory support up to 2^64 LBAs. assumptive 512 computer memory unit sector emulation, most capability of a GPT disk = nine.4 x 10^21 bytes = nine.4 zettabytes (ZB)

Justify Your expertise With Disk Sparing?

SAN Storage array has knowledge integrity engineered into it.

A storage  array uses spares disk drives to require the place of any disk drives that ar blocked as a result of errors. Hot spares are accessible and can spare out predictively once a drive fails.

There are 2 kinds of disk sparing:

Dynamic Sparing: knowledge from the unsuccessful or blocked drive is derived on to the new spare drive from the failing drive

Correction Copy: knowledge is regenerated from the remaining sensible drives within the parity cluster. For RAID 6, RAID 5, and RAID 1, when a unsuccessful disk has been replaced, the info is derived back to its original location, and therefore the spare disk is then accessible.

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What Factors you may think about For coming up with A San?

ISL over Subscription magnitude relation

SAN Fan–in and Fan-Out

Storage Ports

Server I/O Profiles

Fabric options

Continuity necessities

Design ought to address 3 separate levels:

Tier 1: 99.999% availableness (5 minutes of period per year)

Tier 2: 99.9% availableness (8.8 hours average period annually, 13.1 hours maximum)

Tier 3: ninety nine availableness (3.7 days of period per year)

What’s Drooping? a way to Check It?

Drooping= information measure unskillfulness

Drooping begins if:  BB_Credit.

January 25, 2020
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