CommVault Interview Questions – Set 1
Hello, below are few common interview questions that are put together for CommVault.
- Question 1. What Are The Features Of Commvault?
- CommVault software delivers access, protection and sharing for e data reliably, securely and cost effectively whether in the filed, remote site or central office.
- Enhance productivity with secure file sync and share
- Reduce Risk, minimize data leakage, improve data availability and meet compliance requirements
- Simplify Administration with one robust solution for desktop, laptop and server data
- Lower the cost of protection remote and mobile data
- Access protected data from anywhere
- Question 2. What Are Commserve Dr Procedures?
Hardware Fresh: Copy DR Set to Stand by commserve and perform Restore the CS DR set to satand by CS.
DR set can be restored in 2 ways.
- Install Commserve software and perform restore using commserve Disaster Recovery tool GUI. And later perform Name change or
- During Commserve Installtion, Perform Dr Restore from Existing backup.
- Question 3. What Is A Storage Policy?
Storage associates the client Backup to storage Disk or Tape Library. In that copy policy is used to set Retention.
Question 4. What Is Global Dedup Storage Policy?
The global deduplication policy enables deduplication across multiple storage policies that uses a common set of disk libraries and deduplication database (DDB).
- Question 5. What Are The Types Of Copies And What Are They?
There can be only one Primary Copy and Different types of AUXILARY/SECONDARY. The types of copies are.
Selective Copy: A selective copy allows you to copy specific full backup jobs from a source copy, the source copy can be either a primary or a synchronous copy. Selective copy facilitates better tape rotation.
Inline copy: Here Both Primary and Secondary copy are written to storage during Backup Phase itself. Incase if the secondary storage doesn’t have enough space then backup will fail.
Synchronous copy: In synchronous copy all data of primary is copied.
Question 6. What Are The Other Ways Of Doing High Availability?
- Log shipping.
- SQL Mirroring.
- Clustering at SQL Level.
Question 7. How To Move The Ddb To The New Media Agent?
Right-click the mount path, and then click Share Mount Path. point to new Media Agent. Set it to dafault mount Path. If it is a Tape Library configure tape lib and change datapath.
- Question 8. What Is Intellisnap?
It takes a snapshot, and then resumes live operations. IntelliSnap backup works in conjunction with storage arrays to provide snapshot functionality for backup.
- Question 9. What Is The Use Of The Proxy Server?
you can use a proxy server to reduce the load on the production server. The backup copy operation uses the proxy to move the snap to backup media.
- The Storage array is accessed to create a snapshot.
- The snapshot is mounted on the ESX server designated for the snap mount.
- The snapshot is unmounted.
- During the Backup Copy operations:
- The snapshot is mounted to the ESX server designated for the snap mount.
- The mounted snapshot is treated like file system and the required contents are read.
- The file system backup is performed to Primary Copy of the storage policy.
- When the backup copy job is finished, the snapshot is unmounted.
Question 10. What Are Your Day To Day Activities As Backup Admin?
It begins with monitoring the current jobs running in Job controller, Make sure that No job should be in pending & Waiting state without a valid Reason. Also check for suspended and queued Jobs. check if any of the job has got delay reasons, Also check for the Jobs which are running for more than 24 hours. Below are some of the health check tasks.
- check for Media agent, Tape Library(Including Tape Drives) / Disk Library status make sure that none of them are offline.
- Check for the Free space available for Disk Libraries, Index Cache and DDB Paths (Preferable schedule a customized Report for these activites)
- Daily activities
- Extract a backup Report for Failed, Completed with Errors, completed Warnings and Killed jobs (check and act accordingly).
- You may check for Deployment, Decommission, Restores etc if any in ticketing tool.
- Question 11. Can You Tell Me About Your Infrastructure ?
You need to briefly describe about your backup infrastructure and daily activities, for example
We have n(1) Prod commserve m(1) DR/Standy Commserve and n(10-20) pair of Media Aegents and we backup around n(2000) servers which includes Regular file system, Databases like (SQL, Oracle, Exchnage, SAP Oracle, DB2, SAP DB2 etc…). This also includes VMWare snapshot backups (VADP/VCB) / intelli snap. Include all the backups which you perform on daily basis. For Storage we have HUS 150 or HNAS with a total capacity of N(TB)
- Question 12. What Are The Common/regular Backup Failures ?
Some of the common or frequent backup issues are:
- Network Communication issue
- Client services might be down
- Media agent Offline
- Destination Disk Library ful
- Data Path offline
- VSS snapshot backup failure
Question 13. How To Use Only Specific Set Of Tapes For A Server Backup Or For A List Of Server Backup?
Create a new scratch pool and move the required media to new scratch pool and you can set at subclient which scratch pool to be used. you can also do this at storage policy, copy policy level.
Question 14. What Is Difference Between Synthetic Full & Full Backup & Dash Full?
Synthetic full backup consolidates all the incremental backups since last full and appends to make it a full backup. Here the server (Client machine and network utilzation is aslo very low compared to regular full ). Whereas Full backup is a complete full backup taken from server. And Dash full performs copies the unique blocks of the de-duplicated data and updates the DDB and index files to make it a full backup.
- Question 15. What Is Silo (de-duplication To Tape)?
De-duplicated data is copied to tape after the primary de-duplication on Disk this is configured on global-dedup Storage policy.
Question 16. What Is Hash Algorithm?
Hash algorithm is applied on block of data after it is read from client machine and a unique signature is generated which is used to perform De-duplication.
- Question 17. What Is The Default Block Size Set For De-duplication Enabled Storage Policies?
- Question 18. What % Of De-dup Ratio Were You Able To Maintain.?
For File system backups its above 90% and Database backups 70% – 95%
- Question 19. Explain How Vmware Backups Works ?
Vmware snapshots backups are performed using Proxy server. On proxy server VSA (Virtual Server Agent) software is installed. Commvault communicates via Vcenter. Where a snapshot of VM is performed and it is mounted in Proxy server. From proxy the snapshot image is backedup to media agent.
- Question 20. What Are Different Types Of Transport Modes In Vmware Backup And Their Usage?
Transport modes is used to determine which method to be used to mount the snapshot in proxy.
- Transport Mode SAN (storage area network) – SAN mode is supported for directly connected storage. The VSA should have access to the datastore LUNs that provide storage for VM disks. Data is read directly from the storage where VM resides. without going through the ESX host or transferring data over the local area network (LAN). The ESX host is contacted only to coordinate access to the LUN.
- HotAdd In HotAdd mode, the Virtual Server Agent is installed on a VM residing on an ESX Server. In HotAdd mode, the data volumes containing the VMs to be backed up are automatically mounted to the proxy, so they can be accessed by the proxy as a local disk.
- Local Area Network (NBD and NBDSSL) NBD (network block device) & NBDSSL (encrypted NBD) transmit data over the TCP/IP connection between the ESX server and the proxy computer.
NBDSSL is similar to NBD mode, but data transfer between the proxy computer and the ESX server is encrypted.
- Question 21. How You Configure A Cluster Backup?
Create a cluster group and add the client machines in it and perform a sync, For windows during Commvault client software instaltion. It prompts for installtion on passive node(for windows). Perform installation and schedule backup.