Interview Questions.

Question 1. What Is Lun Masking?

Answer :

LUN (Logical Unit Number) Masking is an authorization manner that makes a LUN to be had to a few hosts and unavailable to different hosts.

LUN Masking is applied broadly speaking on the HBA (Host Bus Adapter) stage. LUN Masking carried out at this level is prone to any attack that compromises the HBA. Some storage controllers additionally aid LUN Masking.

Question 2. Why We Need Lun Masking?

Answer :

LUN Masking is crucial because Windows based servers attempt to write extent labels to all to be had LUN’s. This can render the LUN’s unusable by way of other working structures and might result in records loss.

Device overlaying helps you to manage your host HBA access to sure storage arrays devices. A device masking database, based in the storage arrays unit, eliminates conflicts via centralized tracking and get right of entry to statistics. Both HBA and storage arrays director ports of their Channel topology are uniquely recognized by way of a sixty four-bit World Wide Name (WWN). For ease of use, you can companion an ASCII World Wide Name (AWWN) with each WWN.

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Question three. How Will You Ensure That San-connected Tape Devices Are Represented Consistently In A Host Operating System?

Answer :

Use the Persistent Binding for Tape Devices.
Persistent binding is a host-centric enforced manner of directing an working device to assign certain SCSI goal IDs and LUNs.
Persistent Name Binding support is for target devices.
Persistent binding is supplied for customers to companion a certain tool World Wide Port Name (WWPN) to a exact SCSI target ID.
For instance, in which a particular host will usually assign SCSI ID 3 to the primary router it finds, and LUNs 0, 1, and a couple of to the 3-tape drives connected to the router.
Practical examples:

For Emulex HBA on a Solaris host for putting in place chronic binding:

# lputil
MAIN MENU

List Adapters
Adapter Information
Firmware Maintenance
Reset Adapter
Persistent Bindings
Using choice 5 will perform a manual continual binding and the document is: /kernel/drv/lpfc.Conf file.

Lpfc.Conf file seems like:

fcp-bind-WWNN=”50060XY484411 c6c11:lpfc0t1″,
“50060XY4411 c6c12:lpfc1t2”;

sd.Conf record looks as if:
call=”sd” parent=”lpfc” target=1 lun=zero;
name=”sd” figure=”lpfc” goal=2 lun=zero;

Reconfigure:

# touch /reconfigure
# shutdown -y -g0 -i6

Question four. What Is Lun, Logical Unit Number?

Answer :

Logical Unit Number or LUN is a logical reference to whole bodily disk, or a subset of a bigger bodily disk or disk quantity or portion of a garage subsystem.

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Question 5. What Is Wwn Zoning?

Answer :

WWN zoning makes use of call servers within the switches to both permit or block get entry to to precise World Wide Names (WWNs) inside the material. A important advantage of WWN zoning is the capability to recable the material without having to redo the quarter records. WWN zoning is vulnerable to unauthorized access, as the zone may be bypassed if an attacker is capable of spoof the World Wide Name of an authorized HBA.

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Question 6. What Is Port Zoning?

Answer :

Port zoning makes use of physical ports to define safety zones. A user’s access to records is decided through what bodily port he or she is connected to. With port zoning, zone statistics should be updated on every occasion a consumer changes transfer ports. In addition, port zoning does not permit zones to overlap. Port zoning is normally carried out the use of hard zoning, however could also be carried out the usage of soft zoning.

Question 7. What Is The Difference Between Hard And Soft Zoning?

Answer :

Hard zoning is zoning that is applied in hardware.
Soft zoning is zoning that is applied in software.
Hard zoning bodily blocks access to a area from any device out of doors of the region.
Soft zoning makes use of filtering applied in fibre channel switches to prevent ports from being seen from out of doors in their assigned zones. The security vulnerability in smooth zoning is that the ports are still reachable if the consumer in another area correctly guesses the fibre channel address.
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Question eight. Explain The Device Masking Architecture In Storage Arrays?

Answer :

The device covering instructions can help you:

Assign and mask get admission to privileges of hosts and adapters

Connected in a Fibre Channel topology to garage arrays and devices.

Specify the host bus adapters (HBAs) via which a bunch can get admission to garage arrays devices.

Display or list tool overlaying gadgets and their relationships: Typical gadgets are hosts, HBAs, storage arrays gadgets, and Fibre Channel Adapter (FA) ports.

Modify properties, along with names and get entry to privileges related to tool protecting gadgets (as an example, trade the Name of a bunch).

Question 9. How Do You Know What Type Of Fibre Cable Is Needed?

Answer :

Select it on the basis of transmission distance.

If the gap is much less than a couple of miles, I will use multimode fibre cable.

If the space is greater than three-five miles, I will use unmarried mode fibre cable.

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Question 10. How Will You Calculate Raw Capacity?

Answer :

Raw Capacity= Usable + Parity

Question eleven. How Will You Calculate The Required Band Width With Write Operations?

Answer :

The required Bandwidth=the required bandwidth is determined by using measuring the average quantity of write operations and the average size of write operations over a time period.

Automatic Storage Management (ASM) Interview Questions
Question 12. How To Calculate Rpms Of Ssd?

Answer :

SSD drives haven't any movable parts and therefore have no RPM.

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Question thirteen. How Will You Calculate Iops Per Drive?

Answer :

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

a thousand / (Seek Time + Latency) = IOPS

Question 14. Can You Allocate A Lun Larger Than 2.19tb Limit Of Mbr ?

Answer :

Use GPT.

GUID Partition Table, GPT is part of the EFI trendy that defines the layout of the partition desk on a hard pressure. GPT offers redundancy by way of writing the GPT header and partition table at the beginning of the disk and additionally on the give up of the disk.

GPT Uses sixty four-bit LBA for storing Sector numbers. GPT disk can theoretically guide up to two^sixty four LBAs. Assuming 512 byte area emulation, maximum potential of a GPT disk = 9.4 x 10^21 bytes = 9.Four zettabytes (ZB)

Question 15. Explain Your Experience With Disk Sparing?

Answer :

SAN Storage array has facts integrity constructed into it.

A garage  array makes use of spae disk drives to take the area of any disk drives which might be blocked because of errors. Hot spares are available and will spare out predictively while a drive fails.

There are two types of disk sparing:

Dynamic Sparing: Data from the failed or blocked force is copied immediately to the brand new spare pressure from the failing force

Correction Copy: Data is regenerated from the final true drives in the parity organization. For RAID 6, RAID 5, and RAID 1, after a failed disk has been replaced, the facts is copied lower back to its authentic area, and the spare disk is then to be had.

Storage Area Network Interview Questions
Question 16. What Factors You Will Consider For Designing A San?

Answer :

ISL over Subscription Ratio
SAN Fan–in and Fan-Out
Storage Ports
Server I/O Profiles
Fabric Features
Continuity Requirements
Design have to cope with 3 separate ranges:

Tier 1: ninety nine.999% availability (five mins of downtime in step with year)
Tier 2: ninety nine.9% availability (8.Eight hours common downtime in line with yr, thirteen.1 hours most)
Tier three: 99% availability (three.7 days of downtime in step with 12 months)
Question 17. What Is Drooping? How To Check It?

Answer :

Drooping= Bandwidth Inefficiency

Drooping starts if:  BB_Credit<RTT/SF

Where RTT = Round Trip Time

SF = Serialization postpone for a facts frame

Question 18. How Will You Decide How Many Storage Arrays Can Be Attached To A Single Host?

Answer :

use: Fan Out

For instance 10:1.

I will decide this ratio, based totally at the server platform and performance requirement with the aid of consulting Storage companies

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Question 19. What Best Practices You Will Follow To Setup Isl Trunking?

Answer :

I will at once connect collaborating switches byInter-Switch Link (ISL) cables.
I will preserve the Trunk ports in the same port group
I will make sure Trunk ports run at the identical velocity
I will ensure that each one Trunk ports are set to the identical ISL mode (L0 is the default).
I will convert Trunk ports to be E_Ports or EX_Ports
Question 20. Which Load Balancing Policies Are Used Between Inter Switch Links? Explain With An Example?

Answer :

I actually have used Brocade SAN and it has those load balancing rules:

DLS – Dynamic Load Sharing. FSPF link balancing through FSPF routing protocol
DPS – Dynamic Path Selection by way of efficiently striping IOs at SCSI stage
Frame-stage load balancing – Each successive body on a extraordinary bodily ISL.
Question 21. How Will You Calculate Number Of Buffers Required?

Answer :

Number of Buffers: BB_Credit = [port speed] x [round trip time] / [frame size]

Question 22. What Is Buffer-to-buffer Credits?

Answer :

Buffer credit, additionally called buffer-to-buffer credit (BBC) are used as a waft manage method by means of Fibre Channel technology and represent the number of frames a port can store. Fibre Channel interfaces use buffer credits to ensure all packets are added to their destination. Flow-manage mechanism to make sure that Fibre Channel switches do not run out of buffers, so that switches do not drop frames .General overall performance can be boosted via optimizing the buffer-to-buffer credit allotted to every port.

Question 23. For Troubleshooting Have You Collected Logs From A San Switch?

Answer :

Yes. I were using Brocade Fabric and I actually have used “assist keep “to acquire numerous logs for any troubles l2 check the OS log documents/event logs for mistakes:

AIX: errpt -a
Windows: event logs
Solaris: /var/adm/messages
linux: /var/log/messages
HPUX: /var/adm/syslog/syslog.Log
Tru64: /var/adm/syslog
SGI Irix: /var/adm/SYSLOG
ESX: /var/log/vmkernel
ESXi: /var/log/messages

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Question 25. How Will You Calculate Max Iops An Hba Port Can Generate To Any Lun?

Answer :

Max IOPS an HBA Port can generate to any LUN = (Device Queue Depth per LUN * (1 / (Storage Latency in ms/one thousand)))

Question 26. What Is Q-depth? How To Calculate It?

Answer :

The queue intensity is the maximum number of commands that can be queued on the gadget at the identical time.

Question 27. Is The Queue Depth =execution Throttle= Maximum Number Of Simultaneous I/o For Each Lun On A Particular Path To The Storage Port?

Answer :

Calculation of the maximum queue depth: The queue intensity is the number of I/O operations that may be run in parallel on a tool.

Netapps Interview Questions
Question 28. How Will You Calculate Number Of Drives Required?

Answer :

Total Approximate Drives required = (RAID Group IOPS / (Hard Drive Type IOPS)) + Large Random I/O adjustment + Hot Spares + System Drives

Question 29. If You Know I/o Load And Iops, How Will You Calculate How Many Drives Will Be Needed?

Answer :

Total Approximate Drives = (RAID Group IOPS / (Hard Drive Type IOPS)) + Large Random I/O adjustment + Hot Spares + System Drives

Question 30. How Will You Calculate Hdd Capacity?

Answer :

Capacity = Heads X Cylinders X Sectors X Block Size

Question 31. How To Calculate Hdd Capacity?

Answer :

Capacity = Heads X Cylinders X Sectors X Block Size

Question 32. As A San Administrator How Will You Tell Your Boss How Many Drives Are Required For A Requirement?

Answer :

Use the system:

Total Approximate Drives required = (RAID Group IOPS / (Hard Drive Type IOPS)) + Large Random I/O adjustment + Hot Spares + System Drives.

Question 33. You Need To Provision San Storage With A Certain Iops. How Will You Find What Kind Of Disks You Need?

Answer :

Input/output operations in keeping with 2d (IOPS) is the measure of how many input/output operations a garage device can whole inside one 2nd.
IOPS is essential for transaction-based applications.
IOPS overall performance is closely depending on the quantity and sort of disk drives.
To calculate IOPS of a Hard disk force:

1

IOPS = —————————————

(Average Latency) + (Average Seek Time)

To calculate IOPS in a RAID:

(Total Workload IOPS * Percentage of workload that is examine operations) + (Total Workload IOPS * Percentage of workload that is examine operations * RAID IO Penalty)

Automatic Storage Management (ASM) Interview Questions
Question 34. What Are Multi-pathing Schemes And Which One To Use For Optimal Performance?

Answer :

Servers/ hosts uses multipathing for failover from one course to the other when one course from the Servers/host to the SAN becomes unavailable, the host switches to any other path.
Servers/ hosts can also use multipathing for load balancing.
Types of policy:

Most Recently Used: The course utilized by a LUN isn't always be altered unless an occasion instructs the course to alternate. I will use this policy is for Active/Passive arrays and lots of pseudo active/energetic arrays. Most recently used (mru) selects the direction most recently used to ship I/O to a tool.
Fixed: The route used by a LUN is constantly the only marked as favored, until that path is unavailable I use this coverage is for Active/Active arrays. Fixed (constant) makes use of most effective the active direction.
Round Robin: Round robin (rr) uses the mru target choice policy and the any HBA selection coverage to pick out paths.
Custom (custom) units the LUN to expect a custom coverage.
Question 35. With Active- Passive Storage Array What Multipathing Policy You Will Choose?

Answer :

Use Fixed, or Preferred, direction control coverage to intelligently segment workload across each controllers.

Question 36. What Are The Generic Method To Provision San Storage From Any Array?

Answer :

Plan
Validation  with Support Matrix for Host Connectivity
Provide Connectivity
Pick Volumes
Make Meta Volumes if vital
Map out Zoning
Map to storage arrays Ports
Create Zones
LUN Mask
Discover on Server
Storage Area Network Interview Questions
Question 37. How Will You Get The Wwn Of All Your Hba’s To Provision San Storage?

Answer :

AIX
lscfg –v –l fcs#
(fcs – FC Adapter)
SMIT

HP-UX
fcmsutil /dev/td#
(td – Tachyon Adapter)
SAM

WIN:
emulexcfg –emc or
hbanywhere
I can use Storage Explorer to look distinctive statistics about the Fibre Channel host bus adapters (HBAs).

Solaris
/usr/sbin/lpfc/lputil
Also I can use:
more /var/adm/messages greater dmesg

VMware vSphere ESX/ESXi host
There are numerous approaches to get HBA WWNs on VM
vSphere Client;
Using ESXi Shell;
Using Powershell / PowerCLI script.

LINUX
/sys/elegance/scsi_host/hostN/device/fc_host/hostN/port_name
Where “N” is the quantity of device to your fibre HBAs