CommVault Interview Questions

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Q: What is Commvault?
Commvault is a data management platform where your data can be protected using its software products. The software is capable of taking up backups and also has a recovery management process

Q: What are the features of Commvault?
1. The commvault software is entitled to deliver access, protection and sharing of the data in a reliable and in a secure connection.
2. It provides enhanced productivity which has secure file sync system
3. It reduces the risk of data loss with the help of backup software
4. Using this software, it can reduce the cost of protecting remote and mobile data
5. One can access the data from anywhere

Q: Let us know what are the other different ways of doing High availability?
We can do the following:
1. Clustering SQL level
2. Log shipping
3. SQL mirroring

Q: Explain what is a storage policy?
The storage policy usually depends upon the client backup and storage plans. It defines what amount of data needs to be stored and what type of information can be stored. Further, the data stored is in a secured environment or not.  The following are the three different types of copies that are available within the storage policy for commvault:

1. Primary snap copy
2. Primary disk copy
3. Offsite disk/tape copy

Q: What are the types of copies that are available and explain them in detail?
We have only on primary copy and to that, we will be having different types of auxiliary/ secondary types of copies. The list of copies that are available follows:

1. Selective Copy
2. Inline Copy
3. Synchronous Copy

1. Selective Copy:

A selective copy is a process which will allow an individual to copy a specific set backups from a source copy. The source can be one of the following, asynchronous copy or a primary copy.  A selective copy works better for tape rotation.

Inline Copy:

Within this copy phase, both the primary and secondary copies are written to a storage so that it will be available during the backup phase. If the secondary storage doesn’t have the required space then the backup job will fail.

Synchronous copy:

Within synchronous copy process, all the data of the primary is copied over.

Q: Explain the process of moving the DDB to the new media agent?
The following is the process of moving the DDB to the new media agent:

1. Right-click on the mount path option
2. Click on share mount path option
3. Point it towards the new Media agent
4. Set the default mount path
5. Tape library configures and change the data path.

Q: What is Intei snap? Explain the process?
The inteli snap is a process where it takes a snapshot and then it resumes all the live operations.
Intellisnap backup works in line with the storage arrays so that it can provide a snapshot functionality for the backups.

Q: Explain the main use of proxy server?
The use of the proxy server is mainly to reduce the load on the production server. The backup operations generally use the proxy servers to move the snapshot of the information to backup media.

1. The storage array is generally accessed to create a snapshot of the information
2. The snapshot that we can capture is used to mount of the ESX servers which are designated for the snap mount.
3. The snapshot is then unmounted for further utilization.

Q: What happened in Backup copy operations in the proxy server?
During the backup copy operations the following activities are executed:

1. The snapshot of the information is mounted to the ESX server which is solely designated for the snap mount.
2. Once the snap is mounted then it is treated as a file system and the required contents are processed and read
3. The backup of the file system is performed to the Primary copy of the storage policy.
4. Once the backup copy job is finished, then the snapshot will be unmounted.

Q: What are the common/regular backup failures that one experiences most of the time?
Some of the common or more frequent backup issues that are reported as follows:
1.  Network communication issues
2. Client services might be shut down for maintenance
3. Media agent offline
4. Destination disk library full
5. Data path offline
6. VSS snapshot backup failure

Q: How can one use only a specific set of tapes for a server backup or for a list of server backups?
You can create a new scratch pool and all the required media can be moved to the scratch pool. A sub-client is attached to a scratch pool which will be used. This process can also be done at two levels they are:

1. Storage policy level
2. Copy policy level

Q: What is Silo ( de-duplication to Tape)?
First of all the media is de-duplicated onto the disk which is configured on global-dedup storage policy. Once this process is completed when the data is de-duplicated to the tape. Thus the name came up as de-duplication.

Q: Explain what is a hash algorithm?
The hash algorithm is an algorithm which is applied to a specific set of data where the data is read from the client machine and a unique signature is generated which is used to execute the deduplication process.

Q: What is the default block size set for de-duplication which are enabled for storage policies?
The default block size for deduplication which is enabled for storage policies is set to 128KB

Q: What percentage of the deduplication ratio that you were able to maintain so far?
This can be a generalized answer and the ratio that you were able to maintain is as follows:

1. About 90% or more when it comes to file systems backups
2. Between 70% to 95% when it comes to the database backups

Q: Please explain how does a VMware backup works?
The VMware backups are processed in the following manner:

1. Usually, VMware snapshot backups are performed using the proxy servers.
2. Within the proxy server, we will be installing a software called Virtual server agent, i.e. (VSA)
3. So commvault actually communicated via Vcenter.
4. Where a snapshot of VM is performed and it is mounted in proxy server only.
5. From the proxy server, the snapshot image is backed up with the backup process implementation and it will be fed to the media agent.

Q: Explain the process of configuring a cluster backup?
The following process will help an individual to configure a cluster backup:
>> First of all create a cluster group
>> Add all the client machines into it so that a synch action will be performed
>> It prompts for installation on the passive node for windows system.
>> Complete the installation
>> Then schedule a backup process for the same.

Q: What are the different types of transport modes are available in Vmware backup?
The following are different types of transport modes that are available in Vmware backup:
1. Transport Mode SAN
2. HotAdd
3. Local area network

Q: Explain what is Transport mode SAN in detail?
Within this mode:
** SAN model is actually directly connected to a storage system and it is supported.
** The virtual server agent will come into the picture which will have access to the storage system
** Once the data is read from the storage it will remain in Vmware's.
** The ESX host is only connected or coordinates the access to the LUN.

Q: Explain what is the Hotadd mode in detail?
Within this mode:
>> The Virtual server agent is installed on the VM which is actually residing on the actual ESX server.
>> The data is automatically mounted onto a proxy
>> The data that is mounted on the proxy will be accessed as a local disk later on in the process.

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Q: Explain what is Local area network mode in detail?
1. NBD stands for Network block device
2. NBDSSL stands for Encrypted Network block device.

The data is transmitted or passed via a secure TCP/IP connection between the ESX server and the proxy computer. This is the process where the data is passed on within NBD mode.

The above process is same and the data is transmitted via a secure TCP/IP connection between the ESX server and the proxy computer but the data will be encrypted for NBDSSL.

Q: List out all the day-to-day activities of a backup admin?
First thing first, the backup admin will have to monitor whether all the scheduled jobs are running as per they are designated. If not then they have to go through the jobs and understand the fault and rectify the same.

Further, they have to involve themselves with some of the health checkups:

** Have to check for Media agent so that they are not in offline mode
** Have to make sure and regularly check the free space or the remaining space that is available in the disk libraries
** Extract a backup report which is failed and analyze the same so that the rectification process can be continued.
** Check regularly for deployment, decommissions, restores requests within the reporting tool.

Q: Please explain about the infrastructure that you have worked on previously?
This should be an honest reply back to the interviewer because this is a real-time question which can be answered based on the experience available.

I worked in an infrastructure where we had

1 production comm server, 10-20 pair of media agents and have backed up around 200 servers which includes a regular file system.

Q: What is the main product of Commvault?
They are into data protection and information management service businesses. Using their products most of the organizations are helped out with their data and backup and recovery processes with the help of cloud infrastructure and management.

Q: Is commvault software is an enterprise level software?
Yes, it is an enterprise level software.

Using Commvault software is simply because it is built up from scratch and has different modules which can be used independently based on the need.

Q: What does IRM stand for in commvault?
IRM stands for IntelliSnap recovery manager.

It describes all the recovery management concepts within the best practices.

Q: What is the main difference between a clone and a snapshot?
The clone is like a copy of everything that is available within the database. When it comes to Snapshot it is more sort of versioning. So the backups that we take has a certain timestamp. It is similar to that of our restore points in our windows systems. So when the system crashes we have a restore point to start with. The same way snapshots work and this is more catering towards the data availability from a certain point-in-time.

Q: Brief few bullet points on Intellisnap technology?
Intellisnap technology:

1. This technology is developed as lightweight
2. It is a standalone solution which is used for automating snapshot management
3. It is an application-aware where multiple storage arrays can be recovered.
4. It speeds up the recovery management system
5. It helps in maintaining and archiving database snapshots

Q: Where can we access reports in commvault?
All the reports can be accessed within web console or on the clouds server sites and also available in the commcell console.

Q: Explain what is a Commvault appliance?
The commvault appliance is nothing but an end to end solution which helps in extending the data protection aspects and also helps in the storage capabilities using simpana platform.  The commvault appliance provides following benefits, they are:
1. Provides a simple configuration system
2. Provides a simple management system
3. It helps you to meet your enterprise-level data protection requirements.


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