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Commvault^® software provides many features and settings that can improve data protection and recovery performance. It is important to note that, in some cases, these features or settings can have a positive impact in certain aspects, but negative impacts in other aspect.
The following section provides several charts that compare and contrast the pros and cons of features and settings within Commvault software:

Each feature explains potential positive and negative effects on protection windows, media management, and recovery objectives.
Some features may not have any affect or minimal effect so no information is listed.
Each analysis is rated as 'May have', 'Will have', or 'Significant' effect. An explanation is also provided explaining why the effect may occur and which setting causes the effect to take place.
Additional considerations are listed for some features.

The following charts highlights the positive and negative effects of various Commvault protection methods and configuration options. Charts and explanations assume a solid level of competency with the Commvault Product suite.

Storage Policy Configurations

Feature / Option / Implementation Methods	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
Device Streams	May have positive effect by running more jobs concurrently. May have negative effect if infrastructure cannot handle higher data loads. Will have positive effect when used in conjunction with client side deduplication.			Library writers or drives should equal number of storage policy device streams. When using deduplication, ensure Media management 'Maximum number of parallel data transfer operations for deduplication database' is adjusted accordingly.
Erase Data			May have a negative effect on restore as Media Explorer, Catalog or restore by job features cannot be used on media written by an erase data enabled storage policy.
Incremental Storage Policy	May have a positive effect on incremental or log backup performance by writing to a separate disk library.		May have a positive effect on restore performance by restoring inc / logs from fast disk storage.

Primary Copy Configurations

Option / Value	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
Device Streams	May have positive effect by running more jobs concurrently. May have negative effect if infrastructure cannot handle higher data loads. Will have positive effect when used in conjunction with client side deduplication.			Library writers or drives should equal number of storage policy device streams. When using deduplication, ensure Media management 'Maximum number of parallel data transfer operations for deduplication database' is adjusted accordingly.
Multiplexing	Will have positive effect on backups when protecting multiple slower job streams to a single device stream.		May have negative effect on RTO if streams are not required for restore and they are multiplexed to same tape with streams that are required for restore.
Retention		May have negative effect on storage if retention is improperly configured.
Spool Copy	Will have positive effect when first spooling to disk then writing to tape when protecting large amounts of small files.
Extended Retention Rules		May have negative effect on tape consumption if jobs with extended retention are mixed on tape containing jobs with no extended retention. Will have a positive effect on retention when grandfather / father / son tape rotation is required. Significant negative effect if using deduplication. A significant increase for both the disk library size and the deduplication database size that could potentially lead to a deduplication database seal and restart.

Option / Value	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
GridStor™ Round Robin	Will have a positive effect on primary backup by load balancing across multiple MediaAgent.		Will have a negative effect on RTO when using deduplication writing to shared SAN library.
GridStor™ Failover	Will have a positive effect on primary backup by providing a failover path to different MediaAgent, drive pool, scratch pool or library.
Data path chunk size	Will have a positive effect for indexed jobs by increasing chunk size. May have a positive effect for indexed jobs over unreliable network (WAN) by decreasing chunk size.
Data path block size	May have a positive effect on backup performance by increasing block size.		Significant negative effect on restore if hardware does not support higher block size including NIC, HBA, library, drive and MA OS.
Hardware encryption (LTO4 - LTO7)	May have negative effect on backup performance by additional processing to encrypt data.	Provides high level of security.	May have negative effect on restore performance.

Secondary Copies Configurations

Feature / Option	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
Inline copy	May have positive effect by running primary and secondary jobs concurrently. May have negative effect since jobs are streamed and will only run as fast as slowest device.
Combine to streams using tape media	May have a negative effect if configured improperly.	Will have a positive effect on media usage by combining streams to fewer tape media.	May have a negative effect on RTO if streams for restore are mixed with streams not required for restore. Will have negative effect on RTO for multi-stream backups as opposed to placing each stream on separate tape. Note this only applies if using restore by job. Will have negative effect on RTO if different data sets required for restore are on same tape. Only one data set can be restored at a time.
Multiplexing with combine to streams	May have a positive effect if source of auxiliary copy is disk with multiple mount paths.
Software encryption	May have a negative effect on performance depending on MediaAgent resources and size of data in secondary copy.
Using Global Secondary Copy		Significant positive effect on tape usage since many storage policy secondary copies are concatenated on the same set of media.	Significant negative effect on RTO. Less restore jobs can run concurrently as data in stored on same tapes, as opposed to different storage policies tape copies isolated on their own media.

Subclient Configurations

Feature / Option	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
Custom Subclients	Will have positive effect by providing greater scheduling flexibility. Will have positive effect by running multiple streams concurrently.	Will have positive effect by allowing specific content to be retained separately. May have negative effect for secondary copies if stream management settings are improperly configured.
Data readers	Will have positive effect by running multiple streams concurrently.
Multiple readers in drive or mount point	Will have positive effect by running multiple streams concurrently on RAID volumes
Data Streams for SQL, DB2 and Sybase	Will have a positive effect on performance by multi-streaming backup jobs.	May have a negative effect for tape copy since each stream must go to separate tape.	Will have a positive effect on RTO from tape with streams on separate tapes. Significant negative effect if multi-stream backup was combined to tape. Tape copy requires pre-staging to disk prior to recovery.
Filters	Will have a positive effect on backup and auxiliary performance by eliminating unwanted data from jobs.		Will have a positive effect on restores since unwanted data was not backed up. May have a negative effect on restorability if filters are improperly configured and filter important data.
UNC path for file system subclient contents	Will have a negative effect on primary backup. Path will be from UNC share to the Client and then to MediaAgent.

Deduplication Configurations

Feature / Option / Implementation Methods	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
Isolating data in separate policies based on data type and block size	Will have positive effect to improve performance when using multiple MediaAgent using dedicated DDB for each policy. May have negative impact if more than two DDB loaded on single MediaAgent.	May have negative effect with marginal decrease in dedupe efficiency in primary disk storage. May have negative effect for secondary copies if using tape media.	May have positive effect on restore performance by grouping data blocks relative to data type being protected in their own deduplication store folders.	Best practice is to isolate data types to different policies providing greater scalability.
Client side deduplication	Significant positive effect after the first full by sending only change data blocks to MediaAgent. Will have positive effect on secondary copies if using DASH Copy.	Significant positive effect reducing size of data on disk. Will have positive effect on retention by making more efficient use of disk media.	May have negative RTO by slower disk read access (due to fragmentation of data blocks on disk).	For WAN backups using client side deduplication, enable the client side disk cache.
Block size	Larger block size may have positive effect by reducing size of dedupe database making hash comparisons faster.		May have negative effect if using small block size <128k (due to fragmentation of data blocks on disk).	Follow Commvault best practices when determining block size settings.
Compression	May have negative effect due to increase CPU usage on client. Will have positive effect requiring less bandwidth for backup.	May have positive effect since compression adds considerable space savings on deduplication depending on data type.	Will have positive effect on RTO since data is decompressed on client.	Compression takes place before hash so duplicate blocks will generate same hash. If application compresses data, disable compression in dedupe SP.
Feature / Option / Implementation Methods	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
Do not deduplicate against objects older than	Will have negative effect at point specified as all duplicate blocks older than specified number will be backed up again.	Temporary negative effect as duplicate block will be written to dedupe store.		This option is for block integrity by periodically (based on days set) rewrite blocks to disk.
Seal deduplication store	Will have negative effect at point store seals as all blocks will be written to disk.	Temporary negative effect until the old store ages and pruned.		In a well-designed environment sealing the store should not be necessary unless it meets specific protection needs. Sealing the store may become necessary if dedupe database grows too large or if Commvault best practices are not followed.
Global deduplication policy	Will have positive effect on performance by deduplicating against blocks from multiple primary copies into single store. May have significant negative effect on scalability and performance if not configured and implemented correctly.	Will have positive effect on disk consumption by deduplicating blocks from multiple storage policies into single store. May have negative effect since each individual SP will still have to create individual secondary copies requiring dedicated tape for each policy copy.	May have negative effect on performance that may degrade by slower disk read access (due to fragmentation of data blocks on disk).	Global deduplication policies are intended to consolidate remote site backups to a central disk location. This is not intended to centralize data for all policies in an environment.
DASH Full	Significant positive effect on full backups after the first full is performed.
DASH Copy	Significant positive effect on off-site copies to secondary disk target.		Will have positive effect on off-site RPO since data can be copied off-site more frequently versus sending tapes off-site.

SILO Storage Configuration

Feature / Option / Implementation Methods	Protection Windows (Primary / Secondary)	Media Management	Recovery Objectives	Other Considerations
Using SILO	Will have positive effect on performance since data does not require rehydration.	Significant positive effect by writing dedupe data to tape without rehydration. Will have positive effect disk consumption by pruning old volume folders from disk.	May have negative impact on RTO since volume folders must be pre-staged to disk before data can be recovered. May have significant negative effect if large amounts of data need to be recovered. Will have positive effect by copying all dedupe data to SILO it can improve RPO with more recovery points available as opposed to periodically performing full auxiliary copies.
SILO & global deduplication policy		Significantly reduce tape consumption if multiple policies are writing to a global dedupe. Using SILO in place of traditional secondary copies will allow data from multiple storage policies to be stored on fewer tapes. Traditional aux copy would require separate tapes for each secondary copy.	May have negative impact on restore since volume folders must be pre-staged to disk before data can be recovered. May have negative impact on RTO. If large amounts of data need to be recovered, RTO performance can be significantly degraded. Significant positive impact on RPO. By copying all dedupe data to tape, more recovery points will be available as opposed to periodically performing full auxiliary copies.
Number of Silos to be kept in cache		May have a negative impact on storage. Will Increase disk consumption by keeping SILO data in disk cache.	Significant positive effect on RTO. Improve RTO if volumes required for restore are in cache.

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