During a backup job or a restore job, File System clients are slow

A backup job or a restore job of subclient content that contains millions of files is slow.

Symptoms

A backup job or a restore job of a subclient that contains a large number of folders with millions of files under each folder might take a longer time to complete. For example, in the ClRestore.log file, you might notice that the time to open a file is higher:

9800 3b24 06/05 13:41:31 2550287 stat- ID [PL_FS_HDR - Processing Header], Samples [6757908], Time [829928.642209] Sec(s), Average [0.122809] Sec/Sample

Causes

Slow performance is a file system limitation. Some of the factors that can cause slow performance are as follows:

• The generation of short file names.
• Windows Defender or other third-party antivirus and antimalware tools that are installed on the client computer.
• The fragmentation of a large number of index files. When you have a large number of files in a folder, index files are created for the files, and these index files can become fragmented.
• Using Windows Explorer or File Explorer to browse volumes and folders.
• An insufficient amount RAM space to cache the information that is read from the disk.

Resolution

To increase the speed of the backup job or the restore job, you can use the following methods:

• Disable the generation of short file names. For more information, see Microsoft KB Article 121007.
• Turn off Windows Defender or other third-party antivirus software that you installed on the client computer.
• Defragment the index files by using the Microsoft Contig tool.
• If you notice that Windows Explorer occupies a significant amount of space on the CPU, avoid using Windows Explorer during the restore job.
• Increase the amount of RAM to a sufficient amount.