If client backup operations use storage pools that are configured for simultaneous write, the amount of log space that is required for each file increases.
The log space that is required for each file increases by about 200 bytes for each copy storage pool that is used for a simultaneous write operation. In the example in the following table, data is stored to two copy storage pools in addition to a primary storage pool. The estimated log size increases by 400 bytes for each file. If you use the suggested value of 3053 bytes of log space for each file, the total number of required bytes is 3453.
This calculation is used in the example in the following table.
Item | Example values | Description |
---|---|---|
Maximum number of client nodes that back up, archive, or migrate files concurrently at any time | 300 | The number of client nodes that back up, archive, or migrate files every night. |
Files stored during each transaction | 4096 | The default value of the server option TXNGROUPMAX is 4096. |
Log space that is required for each file | 3453 bytes | 3053 bytes plus 200 bytes for each copy storage
pool. The value of 3053 bytes for each file in a transaction represents the log bytes that are needed when backing up files from a Windows client where the file names are 12 - 120 bytes. This value is based on the results of tests performed under laboratory conditions. The tests consisted of backup-archive clients performing backup operations to a random-access disk (DISK) storage pool. DISK pools result in more log use than sequential-access storage pools. Consider a value larger than 3053 bytes if the data being stored has file names that are longer than 12 - 120 bytes. |
Active log: Suggested size | 20 GB 1 | Use the following calculation to determine the size of the active log. One GB equals 1,073,741,824 bytes. (300 clients x 4096 files stored during each transaction x 3453 bytes for each file) ÷ 1,073,741,824 bytes = 4.0 GB Increase that amount by the suggested starting size of 16 GB: 4 + 16 = 20 GB |
Archive log: Suggested size | 60 GB 1 | Because of the requirement to be able to store
archive logs across three server database-backup cycles, multiply
the estimate for the active log by 3 to estimate the archive log requirement: 4 GB x 3 = 12 GB Increase that amount by the suggested starting size of 48 GB: 12 + 48 = 60 GB |
1 The example values
in this table are used only to illustrate how the sizes for active
logs and archive logs are calculated. In a production environment
that does not use deduplication, 16 GB is the suggested minimum size
for an active log. The suggested minimum size for an archive log in
a production environment that does not use deduplication is 48 GB.
If you substitute values from your environment and the results are
larger than 16 GB and 48 GB, use your results to size the active log
and archive log. Monitor your logs and adjust their size if necessary. |