Fast Compression
NOTES:
By default, Fast Compression selects the differential backup after first full, if the amount of changes is less than 35%.
The following table shows how much disk space can be saved for nightly Fast Compression backups for a 100 GB database that changes 5% daily and uses a 35% data change threshold.
Days |
Native backup |
LiteSpeed full backup |
Fast Compression backup |
---|---|---|---|
1 |
100 GB |
20 GB |
20 GB (Full) |
2 |
100 GB |
20 GB |
1 GB (Diff) |
3 |
100 GB |
20 GB |
2 GB (Diff) |
4 |
100 GB |
20 GB |
3 GB (Diff) |
5 |
100 GB |
20 GB |
4 GB (Diff) |
6 |
100 GB |
20 GB |
5 GB (Diff) |
7 |
100 GB |
20 GB |
6 GB (Diff) |
Total: |
700 GB |
140 GB |
41 GB |
To start do one of the following:
Tip: To create Fast Compression jobs or tasks on several instances, create and deploy a LiteSpeed backup template. For more information, see Create Backup Templates.
Fast Compression handles the naming of files automatically. Fast Compression backups have the following format:
where:
NOTE: All indexes start at zero.
Since the database name is incorporated into the backup name, you can safely select the same directory for all databases on an instance. If striping, you can select several directories. Also, you can add directories to mirror the entire backup file to multiple locations.
It is recommended that you create a new folder to use for Fast Compression backups. If you decide to back up to a folder that already has database backups,
Select whether you prefer to create a unique file for each backup or you prefer to manage a single file for each backup set (a backup set is composed of one full database backup plus all associated differential backups):
The Self-Contained Backup Sets option automatically verifies the Full backup exists. The Separate Backup Files option performs the same validation by default.
Note: For cloud backups only "Separate backup files" type is supported. |
You can set the following thresholds to define when to issue a full backup:
Fast Compression measures the amount of data change by either querying SQL Server or by comparing the size of the last differential to the last full backup. The default option is to query actual data pages. It provides the most accurate way to determine the amount of data change. If the query fails for any reason, Fast Compression will automatically run a size comparison to the last Differential backup.
For example, set this parameter to 20%, and should the database change by 20% or more, Fast Compression will automatically run a Full backup. The larger the threshold, the larger the differential backups can grow before Fast Compression triggers the next Full backup.
Regardless of how much underlying database data has changed, when exceeding the maximum interval (in days) between full backups, Fast Compression will force a full backup.
NOTES:
Select the Extension for backup files checkbox to enter or change the backup file name extension. The default is set to bkp.
NOTE: You can select the backup file extension for Fast Compression and make the new default, bak, for new items. For an existing item that does not have an extension defined, bkp is displayed when the item is edited (maintenance plans and templates).
Additionally, you can prevent full backups from occurring on specified days of the week. If you select to exclude specific days of the week from Full backups and Fast Compression is set to execute the first time on an excluded day, assuming no full backup exists that can be used as described above, Fast Compression will not execute a full backup. This will continue until Fast Compression runs on a day that is not excluded.
This option causes LiteSpeed to issue a full backup, if one of the following problems is discovered in the current backup set:
NOTE: If a problem is detected and a full backup is created through escalation, an error will be returned.
Full backup escalation is selected by default to maintain high recoverability level in the situations where recoverability may be limited (missing differential in set) or not available at all (missing full backup). This setting provides insurance against unanticipated errors. For example, if a backup file is missing from the backup set (someone accidentally deleted it), or there is some other type of issue like a Log Sequence Number (LSN) validation error or file corruption, you would not normally be able to restore the database. To correct for this potential issue with backups, Fast Compression automatically runs a full backup to put the database in a restorable state. Errors are still noted in the LiteSpeed UI Console and alerts will still be sent via the job.
If you uncheck this option and Fast Compression discovers an issue, you will have to correct the problem manually. If the physical file for the last full backup cannot be found, a differential backup may be executed successfully, but you will not be able to recover the database using these backups unless the correct full backup is located. Correction may require forcing a full backup using the @ForceFull parameter. xp_slsFastCompression Under normal operating conditions, you should not experience these types of issues as they are normally caused by accidental deletion of files or disk corruption, both of which occur very infrequently.
TIP: "Cleanup" means Smart Cleanup Policies or Smart Cleanup. For more information, refer to Smart Cleanup Policies.
Make sure the backup files in the backup set have integrity. This provides an added level of insurance the backup files can be restored. Verification failures appear in the LiteSpeed UI Console and, optionally, as job failure notifications. A verification failure after a differential backup will trigger the backup escalation process, if selected.
The Verification options include:
The Cleanup options include:
TIP: Use the Ctrl button in Locations browse window to select several locations.
Note: Clean up transaction log options are available if you set up a transaction log within the wizard (or template). |
Cleanup provides a convenient way to remove old backups from disk without disrupting Fast Compression. Select this option to remove full and differential backup files and transaction log backups that are older than the specified time period.
The cleanup routine is backup set aware. This is important because the cleanup will never remove a full backup that is needed by a differential backup that is not being deleted. If you use the Separate Backup Files option in Fast Compression, you have the added flexibility of being able to remove differential backups from the active backup set that are no longer needed.
NOTE: Fast Compression does not raise errors if it detects a missing backup from a backup set that was removed via the cleanup process.
The backup retention will never delete:
For more information, see Smart Cleanup Policies.
Completing the wizard will create the Fast Compression backup job. Using the Backup wizard, you can optionally schedule transaction log backups for the database. Transaction log backups are scheduled as a separate job from Fast Compression.
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