Key performance considerations for NetBackup 7.5 master servers
|Article:TECH202840|||||Created: 2013-02-15|||||Updated: 2013-04-25|||||Article URL http://www.symantec.com/docs/TECH202840|
|NOTE: If you are experiencing this particular known issue, we recommend that you Subscribe to receive email notification each time this article is updated. Subscribers will be the first to learn about any releases, status changes, workarounds or decisions made.|
With NetBackup 7.5, more information is being kept in the embedded relational database. The issues that improve the performance of NetBackup master are outlined in this article.
Status Code: 252 Cannot Connect to Database
Slow Catalog backup
Sluggish or hung NetBackup job throughput
The following are the key factors for reviewing the NetBackup master system health.
Growth of EMM_DATA.db
EMM_DATA.db contains a very small amount of data but is highly transactional. Symantec NetBackup use of isolation levels requires the database to take copies of pages of the database which are marked for cleanup during system quiet times. The database will clean the pages but will not shrink disk space allocated. A large EMM_DATA.db by itself does not indicate an issue. It can be expected that this database grow to around 3GB for customers who have a high volume of backups even if the underlying data is in the MBs. However, growth over 3GB does indicate the system is struggling to maintain an optimal performance. A database rebuild should be performed on databases higher than 3GB to reclaim the space and verify integrity. To rebuild the database, follow the instructions here:
The following performance factors have been known to be the cause of system performance issues and EMM_DATA.db growth.
Many performance improvements are included in NetBackup 184.108.40.206. Customers should download and apply NetBackup 220.127.116.11 to their master server.
(Updated) Customers who continue to exhibit performance/emm_data.db issues after applying 18.104.22.168 are encouraged to call support and request a EEB for ET3123528 which addresses the following issues:
- Use isolation level 'repeatable read' instead of 'serializable' in nbpem
- Removes isolation levels that are not required from several bpdbm queries
- Releases the snapshot isolation queries before calling bpcd removing a potential delay in snapshot clean up
These fixes are required to remove the impact of a Sybase defect which will cause the snapshot isolation table to be maintained inefficiently and cause EMM_DATA.db growth.
The NetBackup fixes and updated Sybase fix will be included in NetBackup 22.214.171.124.
Additional System Configurations:
Semaphore Usage (Unix Masters)
With many process running on the master, it is important to review system semaphore usage and potentially raise the semaphore limits to ensure no semaphore constraints. The following are recommended values:
Recommended sem values:
300 307200 32 1024
More information on configuring these values can be found in the following article:
File Descriptors (Unix Masters)
If the operating system doesn't have enough file descriptors configured, performance will be negatively impacted. File descriptors should be set to a minimum of 8000 and monitored to ensure that value is sufficient on high performing systems. More information on this recommendation can be found here:
Disk performance will have a significant impact on the performance of the NetBackup master. It is required that the average service times for disks NetBackup resides remain lower than 20ms. The following article is a outlines the underlying disk options and requirements:
If disk performance is non-optimal it may be beneficial to move components of NetBackup to different disks to remove I/O contention. The following article outlines the disk layout options for improved performance:
Database Memory Allocation
NetBackup 7.5 allocates initially 1GB of RAM for the underlying database. This can be inadequate and can be adjusted to 30% of available system memory by increasing the -ch value in the server.conf. More information on the location and meaning of the server.conf values can be found in the article below:
Article URL http://www.symantec.com/docs/TECH202840