Tips for troubleshooting slow performance and long running incremental or full backups


Even after trying all the incremental backup types you might have still see a slow incremental backups or sometimes the incremental/full backups get failed in the middle due to insufficient memory (RAM) resources. These kind of issues are generally seen in the windows (mostly 2003) environment if you have large number of files to be backed up in less time. To address this issue, you can use these below methods.

It is recommended to test these backup methods one after another and you should decide which one suits best for your backup window. Also consider the advantages & disadvantages of these methods before taking any decision.

Memory-efficient backup method

Ideally you should first try this option and then try the next methods. Some times the performance of incremental backups can degrade if the system is memory-constrained before the backup begins. Run incremental backup with the memoryefficientbackup yes option in the client options file (dsm.opt). This setting causes the client to process only one directory at a time during incremental backups, which reduces memory consumption but increases backup time.

How it works ?
  • First, the client queries the server for the metadata of active backup versions for the first directory to be backed up.
  • The server returns a list of active backup versions for the directory.
  • The client scans the list and compares it with the local file system, and backs up the new and changed files.
  • The client queries the server for the next directory and repeats the process for all directories.
When to use memory-efficient backup method ?

Use memory-efficient backup when your system has a low amount of memory available for incremental backups.

Also Read: Different types of Incremental Backups

Advantages

Memory-efficient backup is a comprehensive incremental backup with a smaller backup memory usage.

Disadvantages
  • The backup run time will be increased because it has to check each directory one by one.
  • This method does not work for a single directory that contains a large number of files.
  • If the system is enough memory to run regular incremental backups, running memory-efficient backup can degrade the backup performance.

Memory-efficient backup with disk caching

If the client system is memory-constrained and incremental backups still cannot complete successfully even with the memoryefficientbackup yes setting, run incremental backups with the memoryefficientbackup diskcachemethod option. This setting causes the client to use less memory but requires more disk space on the client system. 

How it works ?

This method is similar to incremental backup processing but the client temporarily stores active backup version metadata on disk instead of memory. You have to give the the diskcachelocation c:\ in the option file.

When to use  memory-efficient backup with disk caching ?
  • The client is running out of memory with incremental backups and memory-efficient backup is not sufficient.
  • Journal-based backup is not available on the operating system.
Advantages

Memory-efficient backup with disk caching is a comprehensive incremental backup operation with a smaller backup memory usage.

Disadvantages
  • The backup processing time might be longer because the active backup inventory is on disk instead of in memory. however, in most cases backup will be successfull.
  • Gigabytes of free disk space are required to temporarily cache the active backup inventory

Journal-based backup

Journal-based backup is an alternative form of incremental backup that uses a change journal that is maintained by the Tivoli Storage Manager journal process. On Windows clients, the change journal is maintained by a journal service. On AIX and Linux clients, the change journal is maintained by a journal daemon process.

How it works ?
  • Journal-based backup processing uses real-time monitoring of a file system for changed files all the day.
  • The names of the changed files are then logged to the journal database.
  • During backup processing, the client queries the journal for the list of changed files, and then backs up the changed files.

When to use Journal based backup ?
  • When the scheduled backups are not completed within the allotted time even after trying memory efficient backup methods.
  • When there are less than 1,000,000 files and a small number of changes between backups (less than 1,000,000).
  • When there are less than 10,000,000 objects with 10-15% velocity of change. The velocity of change means the rate at which files are changed over a short amount of time (such 1 or 2 seconds).
Advantages

Journal-based backup can often greatly reduce the time that it takes to determine which files changed.

Disadvantages
  • You must still run incremental backups periodically.
  • Journal-based backups are not suitable for file systems where large numbers of files can change over a short time interval, such as changing hundreds or thousands of files in 1 or 2 seconds.
  • This method is available only on Windows, AIX, and Linux clients.




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