Commvault Interview Questions for Freshers

1. What is Commvault in the context of Application Software?

Commvault is a data protection solution for medium and large businesses and is in extreme demand today. To handle an application’s disaster recovery and data protection activities, it offers an exceptionally flexible web user interface. It minimises the time it takes to perform routine data recovery and protection operations by using default simplified methods and configuration parameters. We can identify the stuff we want to secure and start and control restores and backups using Commvault's command centre.

Leading multinational corporations such as Adobe, Apollo Tyres, Microsoft, NTT DATA, and NASA rely on Commvault to manage their rapidly changing business environments. The latest Commvault features streamline the data backup and recovery processes.

2. What are the advantages of using Commvault?

The following are the advantages of using Commvault:

• Storage: Data can be securely stored on tape, disk, and database servers. We can employ data autonomous multiple copy management to meet all compliance and disaster recovery requirements.
• Access to data and information: We can access and save emails and data files, as well as assist in retrieving and recovering them on a constant basis from mobile and online browser sites.
• Changing, analysing, and reporting: To give a full review to the CommCell, Commvault modifies the events that require attention, reports with in-depth information on the operations, and detailed data analytics.
• Data Security: All of the major applications and operating systems provide data protection methods such as archiving, replication, backup, and snapshots.
• Administration: A single administration interface is used to manage all administrative tasks. Web pages and mobile devices can be used to perform the tasks.

3. What are the key features of Commvault?

The key features of Commvault are as follows:

• Provides Backup: Virtual machines, applications (including cloud), databases, endpoints, and files are all protected by backups. This has the following benefits:
  • Customized schedules to satisfy any SLA with policy-driven automation, monitoring, and reporting; no tedious scripts are required.
  • Data that has been deduplicated for faster data transmission.
  • Auto-discovery protects newly uploaded data sets in a proactive manner.
  • Customized retention for compliance and recovery.
  • Encryption at rest and in transport can be configured.
• Provides recovery: Recovery of virtual machines, apps (including cloud), databases, endpoints, and files is ensured. This has the following benefits: 
  • Recovery of the full system, instance, or application.
  • Granular single file recovery.
  • In-place or out-of-place to a different location.
• Enables migration: Workload migration from on-premises to cloud, or between clouds is enabled. This has the following benefits:
  • Minimal need for customised scripts. 
  • No downtime for production systems.
  • Data portability between clouds. 
  • Avoids vendor lock-in.
• Integration of hardware snapshots: Commvault leverages hardware snapshots for near-instant recovery of full data volumes. This has the following benefits:
  • Support for all major snapshot hardware vendors.
  • Automated snapshot backup and recovery. 
  • Customized snapshot retention.
• Integration with the cloud: We can use the cloud for scalability, mobility, availability, and cost savings for production workloads. Commvault has the following benefits with regards to this:
  • Support for all major cloud vendors.
  • Backup, recovery, and migration to, in, and from the cloud on a single platform.
  • Maintain compliance control on both on-premises and cloud data management.
• Flexible storage options: We can have multiple copies of data in multiple locations. Commvault has the following benefits with regards to this:
  • Disk library – individual hard drives or RAID array. 
  • Tape library.
  • Cloud storage – all major suppliers supported. 
  • Network-attached storage (NAS).
  • Deduplication for more efficient – and cost-effective – data storage.

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4. What do you know about the Deduplication Database in the context of Commvault?

In Commvault, whenever a storage policy with deduplication is implemented, signatures are generated for data blocks during backups, compared, and then stored in the deduplication database (DDB). The DDB backup subclient automatically protects DDBs. All active DDBs controlled by the MediaAgent that hosts the DDB are backed up by this subclient. You can set up a reconstruction task for an automatic or on-demand restore of the DDB from the DDB backup in the event of DDB failure. The storage metadata can then be used to rebuild missing records.

5. What are the various types of transport modes that VMware supports?

• Storage Area Networks (SAN): The VMware Backup Host must be installed on a physical computer that has access to a Fibre Channel or iSCSI SAN that contains the virtual discs to be accessed. Because no data must be sent through the production ESX/ESXi host, this is an efficient data channel. In this mode, the vStorage APIs get information about the structure of VMFS LUNs from the vCenter server or the ESX/ESXi host and then read data directly from the SAN or iSCSI LUN where the VMDK is stored.
• Local Area Network (LAN): The ESX/ESXi host reads data from storage and transmits it via a network to the VMware Backup Host in this mode. Unlike SAN transfer, this kind of transport does require a LAN. The following are some of the benefits of LAN transport:
  • Any storage device, whether local storage or NAS, can be used by the ESX/ESXi host.
  • Because the VMware Backup server could be a virtual machine, you can use VMware vSphere's resource pool and scheduling capabilities to reduce the backup's performance impact. You can put the VMware Backup Host, for example, in a different resource pool than the production ESX/ESXi hosts, with a lower backup priority.
  • If the ESX/ESXi host and the VMware Backup Host are on the same private network, you can use unencrypted data transfer instead of NBDSSL, which is faster and uses fewer resources. You can transport virtual machine data in an encrypted form using NBDSSL if you need to protect sensitive information.
• HotAdd: When running VMware Backup Host on a Virtual Machine, vStorage APIs can use the ESX/ESXi server's SCSI Hot-add feature to attach the VMDKs of a backed-up Virtual Machine to the VMware Backup Host. It's simple to move a virtual machine around, and it can back up local storage without utilising the LAN, however, this has a higher burden on the physical ESX/ESXi host than using SAN transport mode.
• Network Attached Storage (NAS): The VSA proxy computer can read data directly from the network file server using NAS.

6. Write a list of all the tasks that a backup administrator performs on a daily basis.

First and foremost, the backup administrator must ensure that all planned jobs are operating as expected. If they don't, they'll have to go over the work again to figure out what's wrong and how to fix it.

They must also participate in some of the following checkups:

• Check for Media agents to make sure they aren't in offline mode.
• To monitor the free space or remaining space in the disc libraries on a frequent basis.
• Extract a failed backup report and examine it so that the rectification process can continue.
• Check the reporting tool on a frequent basis for the deployment, decommissioning, and restoration requests.

7. What are some of the most common/regular backup failures that one encounters?

The following are some of the more common or more frequent backup issues:

• Network communication issues.
• Destination disk library full.
• Client services might be shut down for maintenance.
• Media agent offline.
• VSS snapshot backup failure.
• Data path offline.

8. Explain the following terminologies in the context of Commvault: IRM CommCell, CommServe, CommServe Database, CommCell Console, MediaAgent, IRM Clients.

• IRM CommCell: The IRM CommCell, which is based on the Microsoft Windows platform and Microsoft's SQL Server Express, consolidates all task management functions, metadata, scheduling, and reporting into a single console. The CommServe application and the MediaAgent are two standard components in this IRM CommCell. These two components share a single operating area known as a CommCell.
• CommServe: CommServe is the master server in charge of CommCell's configuration and operations. It runs on a Windows host server and includes an embedded version of Microsoft SQL Express, which serves as IRM's top-level database. Each CommCell has one CommServe, which must be available to run operations. The CommServe handles only job control and metadata. The MediaAgent specified in the CommCell is used to perform indexing and snapshot management.
• CommServe Database: The CommServe Database is built on Microsoft SQL Express Edition and contains all of the CommServe's history and usage. Information such as work history, client settings, media type, and so on are all maintained in the database, and every item of data that is retrieved, saved, or deleted is recorded in the CommServe database.
• CommCell Console: It is the console that contains all of the CommCell environment's administration features and capabilities in a single pane. The console is java-based and may be launched as a local console instance or accessible through a browser from anywhere. In this console, all policies, operations, scheduling, alerting, and reporting are integrated and displayed to users depending on their security permissions and roles.
• MediaAgent: The MediaAgent is a data mover and indexing resource in a data management environment's data movement workflow. This component plays a variety of roles in the creation/mounting of snapshots and the cataloguing of client-relevant material. The MediaAgent will also act as the disc library's media library manager, storing index data. Those indexes are stored in the Archive file format, so they can't be mounted or used directly; instead, you'll need to do a restore to get a native recovery copy of the data.

• IRM Clients: In IRM, clients are servers and systems that use snapshot integration with production storage arrays. Each server will have a base File System iDataAgent installed to facilitate essential connectivity with the CommServe. You can then load more iDataAgents for application integration or VMware integration, depending on the information or data you want to safeguard. These agents provide the appropriate level of integration for File Systems, Databases, Exchange, SQL, and VMware guests to guarantee that the necessary data is secured at the appropriate level.
  These agents will also ensure that VSS writers are properly called to ensure that the data in the snapshot at the point-in-time is consistent, that "ESEUtil" commands can be used to check Exchange Database consistency, and that VMware calls the appropriate software quiescing mechanisms to create consistent VMs.

9. For deduplicated storage policy, what is the default block size?

For deduplicated storage policies, the default block size is 128kb.

10. What do you understand by a snapshot in the context of Commvault? What are the advantages of having snapshots?

A snapshot is a "picture" of your server's file system taken at a certain point in time. In the event of data loss or corruption, this picture of your file system is frequently utilised to recover complete servers. When there isn't enough space, fresh snapshots will typically overwrite existing snapshots. Snapshots can come in handy in a variety of situations.

The following are the advantages of having a snapshot:

• Snapshots are tiny and can be taken quickly and simply without causing too much server load.
• They improve app availability, speed recovery, simplify backup administration for large data volumes, and reduce data loss risk.
• Snapshots can be scheduled and used for system backup as needed.
• They can almost completely eliminate the requirement for backup windows while also lowering the total cost of ownership.
• Snapshots can be used to recover data that has been corrupted or destroyed. (In the event of file corruption, you can also roll back to an older version of a snapshot.)
• Rather than restoring the entire system, replicated snapshot copies can be used because they are already in their natural format.
• You can immediately begin restoring a server from a snapshot.

11. Explain the differences between snapshot and backup.

• Backup: A backup is a copy of a file or other piece of data. When you start a backup, it copies your files. These duplicates are stored in a different location. Depending on the amount of data you're backing up, backups can take a long time to complete.
• Snapshot: Snapshots are a kind of "picture" of your server's file system that you can take at any time. This picture accurately depicts the server at the time it was taken. Servers can be restored using snapshots by restoring them to the state they were in when the snapshot was taken.

The following points illustrate the differences between snapshot and backup:

• Backups can be kept in multiple places, on the same disk, or even on the same server. They don't necessitate both off- and on-site storage. Snapshots necessitate both on-site and off-site storage, and they must always be kept in the same locations as the original system data.
• Backups for SQL servers are normally done through a subscription service. The operations involved in creating snapshots are normally free and can be done at any time.
• When it comes to backups, there can be discrepancies between when they started and when they finished. Snapshots are "pictures" of your server that retain it in its current state.
• Making backups can be a time-consuming and laborious task. Snapshots are instantaneous and take a fraction of the time. Snapshots also save time when copying data.
• Only the file system is included in backup files. Different types of systems can be captured in snapshots. Files, programs, settings, and other items fall into this category.
• Backups are saved in various locations and can be readily recovered. Backups are frequently verifiable as well. Snapshots aren't the same thing as backups. They can (and should) be utilised as a part of the backup process, but they are primarily short-term solutions. When a backup is finished, snapshots are removed.

12. How can you know if a job has been encrypted, and if so, how?

For jobs that have been software or hardware encrypted, a superscript E or a HE will appear next to the job ID in the Jobs in Storage Policy report.

13. How much of a performance hit can you expect as a result of encryption?

Software encryption is a CPU-intensive activity that can slow down your backup or supplemental copy by 40 per cent to 50 percent. This projected performance hit does not apply to deduplicated data because the deduplication process removes all duplicate data and only encrypts data blocks that are unique throughout the whole deduplication database. As a result, the performance impact of deduplicated data will be minimal.

14. How are keys backed up in the event of a disaster?

Disaster Recovery protection is provided through a regularly scheduled Export and Backup of the CommServe Database (DR Backup activity).

15. Who is in possession of the encryption keys?

The encryption keys are not accessible to anyone. These keys are encrypted with the client's RSA public key and kept in the CommServe database. Depending on the settings, the client's RSA private key is encrypted with either a built-in passphrase or a passphrase provided by the user. The Pass Phrase entered by the user is not saved. These passphrases can only be set and changed by authorised users (as determined by user management). Passphrases are never written down in plain text.

16. Where are Pass Phrases stored in Commvault?

Pass-phrases are not saved. For each recovery, the user must manually enter the pass-phrase. The system, on the other hand, can recover the client's data to that (and only that) machine by producing and exporting a file that contains the scrambled pass-phrase of the client's computer to a designated directory on another computer.

Commvault Interview Questions for Experienced

17. What events are triggered during a Deduplication Database (DDB) backup process?

The following events occur when the DDB backup job starts:

• For a few seconds, all communication with the active DDB is halted. To ensure that the DDB is in a dormant stage, the information in memory is committed to memory.
• The DDB process uses VSS (Windows) or LVM (Linux) snapshots to make a snapshot of the volume.
• The file systems Extended 3 File System (ext3) and VERITAS Volume Manager (VxVM) are also supported on the Linux platform.
• All communication with the DDB is resumed when the snapshot is created, and the DDB is automatically backed up from that snapshot.
• If a VSS (Windows) or LVM (Linux) snapshot fails, the DDB backup falls back on a live volume backup. 
• The snapshot is erased after a successful DDB backup. The Job Controller displays the DDB Backup job in a running condition at this point.
• If the DDB MediaAgent restarts during a DDB backup job, the job is marked as Pending. The DDB backup job resumes from the beginning after the restart.
• The DDB backup jobs for the auxiliary copy operation are disabled by default, and these jobs appear as unavailable when viewed from the primary copy.
• Allowing DDB Backup Tasks from Being Copied to Secondary Copy describes how to enable or prohibit DDB backup jobs from being copied to secondary copy during the auxiliary copy procedure.

18. Explain the following terminologies in the context of Commvault: Storage Policy, Job Manager, Backup set, Subclient, Collect Files.

• Storage Policy: The storage policy determines where the data is saved and how long the snapshot will be kept. Copies can be found within a Storage Policy. In the IRM environment, these copies define retention for the designated storage devices. Within IRM, there are just two versions of interest. The Primary Snapshot Copy and the Primary Copy are two different copies of the same thing. The Primary Snapshot Copy merely specifies how long the snapshots will be kept and which MediaAgent will be cataloguing them. The Primary Copy specifies the location of the catalogued indexes.
• Job Manager: Displays all information about a running job, including data protection, recovery, and Auxiliary copy, as well as settings and media usage. Snapshot jobs can be launched, suspended, restarted, and cancelled by the Job Manager.
• Backup Set: A backup set is a sub-container present within each of these agents. The backup set is the client's overall container. The most straightforward approach to comprehending a backup set is to relate it to the context of the system being snapped in the environment. The backup set for the file system iDataAgent is the fundamental physical system storage environment, whereas the backup set for these two database agents is the Exchange Information Store or SQL instance. An overall vCenter is the backup set in a Virtual Context since it encompasses numerous ESX servers that house and manage virtual machines.
• Subclient: The smallest subset of a client is called a subclient. From the perspective of a Windows host, it may be a single folder, a single database, a single Virtual machine, or a single LUN or drive letter (regardless of how many LUNs are meta-LUN'ed to produce one huge LUN pool). Sub clients are backup set definitions that are related to Storage Policies, which define the snapshot data's retention and location.
• Collect Files: During an IntelliSnap job, Collect Files are smaller text files that will gather information on what is on each of the clone/snapshots. The original information lying on the snapshots is indexed by the collect files saved under the task result directory under each of the IRM clients when the snapshot is mounted to be catalogued. Once the cataloguing is complete, the information will be given immediately to the MediaAgent who will store it in indexes for a longer period of time. These indexes will remain on the MediaAgent for the duration of the snapshot's retention period, either in the local MediaAgent index cache or in the disc library set up to protect the indexes and the CommCell database backup.

19. What is the difference between a snapshot and a clone of a virtual machine?

A snapshot copies the virtual machine's disk file to maintain its current state. It is used as a backup system. Create a snapshot if you need to save the configuration of a virtual machine so you can revert to it later if something goes wrong. A clone, on the other hand, is a complete copy of the virtual machine. Cloning is the sole option if you need to create a new virtual machine that will run on its own.

20. Is a Certificate Authority required for encryption in Commvault?

Only in the case of asymmetric cryptography, where distinct keys are used to encrypt (with the private key) and decrypt (with the public key), is a Certificate Authority required. There is no need for a certificate or a certificate authority because all of our encryption is symmetric (the same key is used to encrypt and decrypt).

When exchanging data over insecure lines (such as the internet), and the identity of the entities on both ends is unknown, asymmetric crypto is employed. The CA helps validate the validity of the sent data, ensuring that malicious material is not sent. This issue does not exist in our situation because both endpoints have known entities.

21. When writing to the media, can encryption have an effect on compression?

Yes, data is effectively randomised when backup procedures are performed using encryption. This means that while compressing encrypted data, compression methods will be less effective. As a result, there will be a visible difference in the compression ratio when this data is written to the media.

For example, a tape with a native capacity of 110GB that was formerly compressed to 190GB may now only be able to write 124GB to the same tape when encryption is used. The amount of data that can be written to tape depends on the type of data that is being written. Image files will not be compressed because they are already compressed, however, a TXT file will be compressed heavily.

22. Is the data encrypted twice if you enable encryption during backup and offline/auxiliary copy?

No, the data is not double-encrypted. Data that has been encrypted by HDPS Monitor software is flagged. The flag is checked during an auxiliary copy operation, and if the data has already been encrypted, no additional software encryption is used. During the auxiliary copy procedure, only data that has not been encrypted by HDPS will be encrypted.

23. In the CommServe database, how are keys stored?

Data encryption keys are encrypted with the client's RSA public key and stored in the database. Depending on the settings, the client's RSA private key is encrypted with either a built-in passphrase or a passphrase provided by the user.

24. What are the different kinds of copies in the context of Commvault and what do they mean?

In Commvault, only one primary copy and many sorts of auxiliary/secondary copies are permitted. There are various types of copies.

• Selective Copy: You can copy specified full backup jobs from a source copy, which can be either a primary or a synchronous copy. Selective copy allows for more efficient tape rotation.
• Inline copy: During the Backup Phase, both the Primary and Secondary copies are written to storage. Backups will fail if the secondary storage does not have adequate space.
• Synchronous copy: A synchronous copy copies all of the data from the primary.

Useful Interview Preparation Resources

• CommVault Documentation
• VMware Interview Questions
• Technical Interview Questions
• Coding Interview Questions

Frequently Asked Questions

25. Why do you want to join Commvault?

This is a behavioural question. Here the interviewer assesses your interests and your desire to join the company. Your answer must clearly depict what motivates you in working at Commvault. 

A sample answer to this could be like this: “I have always been fascinated by data. Since Commvault focuses on data backup and recovery, I feel that I will be highly enthusiastic while working here. I am hopeful of a steep learning curve at Commvault and I strongly believe that this will give a boost to my career. Besides, I have interacted with a few people working at Commvault. They are extremely happy with their job. All of these motivate me to join Commvault.”

26. How do I get into Commvault?

To get a job at Commvault, the candidates are required to go through a hiring process. The hiring process consists of the following rounds:

• Online Coding Round 1: The coding round is typically a 1 hour long round and it usually consists of 10 - 15 MCQs and 2 - 3 coding questions. The MCQs are based on computer fundamentals like Operating Systems, Object-Oriented Programming, Database Management Systems and Computer Networks. 
• Coding Round 2: The candidates who clear the online coding round have to go through one more coding round. This round assesses a candidate’s data structures and algorithms knowledge as well as system design skills. This round is a long one, usually ranging from 5 to 7 hours. Candidates are connected with mentors who can help them while they are designing.
• Technical Interview Rounds: The candidates who clear the online coding round are then required to appear for face-to-face technical interview rounds. Usually, at Commvault the candidates are required to go through 1 technical round. Here the interviewer assesses the technical skills of the candidate. You can expect questions based on computer fundamentals like Object-Oriented Programming, Database Management Systems, Operating Systems, Computer Networks and coding questions based on data structures and algorithms. 
• HR Round: The candidates who clear the above rounds need to go through one last HR round. Here the interviewer assesses whether or not the candidate is a cultural fit for the company. 

27. Is Commvault a product based company?

Yes, Commvault is a product based company.

28. How much do CommVault software developers in India get paid?

The typical salary for a software developer at Commvault ranges from 13 lakhs to 15 lakhs per annum.