A chunk is the unit of data that the MediaAgent software uses to store data on media. For Sequential access media, chunk is defined as data between two file markers. By default, the chunk size is configured to get the optimal throughput to the storage media.
The following table gives default chunk size for tape and disk backups and the recommended range of chunk size:
|
Storage Media |
Backup Type |
Default Chunk Size |
Recommended Range of Chunk Size |
|---|---|---|---|
|
Tape |
Granular Backup |
8 GB* |
8 GB, 16 GB, 32 GB |
|
Database Backup |
16 GB |
8 GB, 16 GB, 32 GB |
|
|
Disk |
All Backups |
4 GB* |
---- |
|
Cloud |
All Backups |
4 GB |
---- |
|
Amazon Glacier (Direct Glacier) |
32 GB |
---- |
|
|
Direct Attached NDMP |
All backups |
16 GB |
---- |
|
Scaleout Storage |
All backups |
8 GB |
---- |
* The default chunk size for NDMP backups is 16GB. Even though a higher chunk size increases the throughput. granular restores (for example, single file restore) become slower. However, large restores, like a full-machine rebuild, become a bit faster.
We recommend a lower value for frequent checks of slower backups, especially when data is moving across a WAN link.