Description
The Accelerator track log stores filesystem metadata and unique fingerprints of files (128KiB segments).
The track log size is relative to the size of the filesystem and the number of files being backed up. There are different track logs created for each policy/client combination.
The following are only guidelines and requirements in a specific environment might be different. Environments with a high rate of data change may require a larger track log size.
Agent backups:
For agent based backups, the track log is stored on the client. The following formula can be used to calculate the approximate size:
Track log Size in Bytes = 2*( (Number of files * 200) + ((Total used disk space in KiB/128KiB) * 20))
Example of 1 TB file system with one million files = ~ 701 MiB track log
NDMP backups:
As NDMP backups do not require a client install, the track log is created on the Master and Media Server for each policy/client combination. The following formula can be used to calculate the approximate size:
Track log Size in Bytes = (number of files * 128) + (((total disk space used) / 128KiB) * 20)
VMware backups:
VMware backups do not use a track log, instead state files are created on the Backup Host. The state file stores information about each extent of data on a virtual disk:
- 24 bytes are needed per extent.
- The number of extents per virtual disk depends upon disk fragmentation, allocation type, and other factors.
- In practice, there are 1-3 KiB of state file for every GiB of virtual disk.
State files are cleaned up when image is expired
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