The NSS salvage system makes it possible to retain deleted files for a specified period of time or until space is needed. The volume salvage and file salvage subsystems function separately.
For volume salvage, the NSS volumes are automatically retained on deletion. The deleted volume can be salvaged for a period of time that is determined by the server-level Logical Volume Purge Delay setting. Administrators with the Supervisor right can salvage or purge deleted volumes at any time before the purge delay elapses.
Table 24-1 describes parameters that control the volume salvage behavior for NSS volumes. The server-level settings apply to directories and files on all NSS volumes.
Table 24-1 Volume Salvage Parameters
|
Salvage Policy |
Range of Influence |
Refer to |
|---|---|---|
|
Logical Volume Purge Delay |
Server-level Default: 345600 seconds (4 days) The automatic purging delay applies to deleted NSS volumes. |
Section 24.2.1, Setting the Purge Delay for All Deleted Volumes |
|
Logical Volume Purge Delay After Continue |
Server-level Default: 900 seconds Seconds to delay purging a deleted volume after a continue. |
Section 24.2.1, Setting the Purge Delay for All Deleted Volumes |
|
Logical Volume Purge Delay After Load |
Server-level Default: 7200 seconds Seconds to delay purging a deleted volume after an NSS load if the purge delay elapses while NSS is disabled. |
Section 24.2.1, Setting the Purge Delay for All Deleted Volumes |
Auto Purging of Logical Volumes: The auto purging of logical volumes is determined by all the above mentioned volume salvage parameters. For example, you have deleted a volume and set the following parameters for auto purging:
LogicalVolumePurgeDelay: 7:24:16 p.m.
LogicalVolumePurgeAfterContinue: 7:39:06 p.m.
LogicalVolumePurgeAfterLoad: 7:20:00 p.m.
The latest time is considered for auto purging. Therefore, the volume is purged at 7:39:06 p.m.
Salvage for directories and files is controlled by each volume’s Salvage attribute. You can enable the Salvage attribute when you create the volume, or modify the setting later in the volume’s properties. Deleted directories and files are retained and can be salvaged until space is needed in the pool where the volume resides, as determined by the pool’s available-space watermark settings. The administrator user or any user who is a trustee with the Create right can salvage deleted directories and files.
Table 24-2 describes parameters that control the file-system salvage behavior for NSS volumes.
Table 24-2 Files Salvage Parameters
|
Salvage Policy |
Range of Influence |
Refer to |
|---|---|---|
|
Salvage attribute |
Volume-level Default: Enabled |
Section 24.3, Enabling or Disabling the Salvage Attribute for an NSS Volume |
|
Immediate Purge of Deleted Files |
Server-level Default: Disabled |
Section 24.2.2, Setting the Immediate Purge of Deleted Files for All NSS Volumes |
|
Low and High Watermarks |
Pool-level Default: low 10%; high 20% Volume-level watermarks are not available. |
|
|
Purge Immediate file system attribute |
Individual directory or file where the attribute is enabled. |
Section 24.2.4, Setting the Purge Immediate Attribute for a Directory or File |
When you salvage a volume, the data and metadata is exactly the same as it was at delete time, with no changes.When salvaging deleted directories or files, the content, trustees, trustee rights, and the inherited rights filters are just as they were before the file was deleted. If the rights in the tree above the salvaged file have changed, then the inherited rights for the salvaged deleted file are calculated based on the current rights above it in the directory tree.
Purging is triggered to begin by the following events. After the deleted data enters a Purge state by manually starting a purge or by autopurging, deleted files can no longer be salvaged (do not return to a Salvageable state), even if you pause the autopurging process.
The Logical Volume Purge Delay setting times out for a deleted volume. Autopurging begins automatically and can take some time, depending on the size of the volume.
The elapsed time between the delete and the purge is called the purge delay. The server-level LogicalVolumePurgeDelay parameter applies to all NSS volumes. For information, see Section 24.2.1, Setting the Purge Delay for All Deleted Volumes.
The pool’s Low Salvage Watermark setting is reached, indicating that the amount of free space is below the administrator-specified minimum. NSS automatically purges the deleted files and directories for all volumes in the pool with a first deleted, first purged policy until the free space reaches the high watermark, or until all of the existing deleted directories and files are purged, whichever occurs first.
You configure thresholds for space-based purging on each pool. Low and high watermarks determine when to begin and stop automatic purging of deleted files to free up space on the pool. For information, see Section 24.2.3, Setting the Low and High Salvage Watermarks for Automatically Purging Deleted Directories and Files.
A user or administrator purges the deleted file or directory.
Deleted directories and files can be purged by the administrator user or by any user who is a trustee with the Erase right at any time before the automatic purge begins. For information, see Section 24.5.3, Purging the Deleted Files.
An administrator purges the deleted volume.
Delete volumes can be purged by the administrator with Supervisor right to the volume. For information, see Section 24.5.3, Purging the Deleted Files.
Salvage is disabled at the server level for directories and files.
Directories and files are purged immediately on deletion if the server-level ImmediatePurgeOfDeletedFiles parameter is enabled. If the Salvage attribute is enabled for a volume, this setting overrides it. For information, see Section 24.2.2, Setting the Immediate Purge of Deleted Files for All NSS Volumes.
Salvage is disabled for the individual directory or file.
If the Salvage attribute is enabled for an NSS volume, you can set the PurgeImmediate file-system attribute on individual directories and files so that they are purged immediately on deletion. For information, see Section 24.2.4, Setting the Purge Immediate Attribute for a Directory or File.