19.2 Configuring Salvage for the NSS Volume
In NSS, there is no separate salvage area as there is for NetWare® Traditional volumes. The metadata for the deleted file or directory is marked as deleted, but its metadata and data remain in the same physical location until the space is needed or until the file is salvaged. Because the file structure information is available in metadata, you can salvage deleted files in an existing directory, or salvage a deleted directory to make its deleted files available for salvage.
In comparison, when you delete a file on a Traditional NetWare® volume, the deleted file is moved into the deleted.sav directory, which is known as the file salvage area. No record is kept of where the file originated, so salvaging files by their original directory is not possible.
NOTE:When you migrate files from a Traditional volume to an NSS volume, the deleted.sav directory and its contents are not migrated; thus, they are essentially purged. If you upgrade a Traditional NetWare volume to an NSS volume, make sure to salvage any deleted files you want to keep before the migration.
NSS tracks how much space is used and determines when to purge files based on the settings for the purge delay, low watermark, and high watermark parameters for an NSS volume. Files are purged on first-deleted-first-purged basis. You can salvage or purge deleted files and directories on demand.
19.2.1 Setting the Purge Delay
The Purge Delay setting for the NSS volume determines the amount of time (in seconds) that you can still access the deleted volume before it is removed from the system. The default value for the Purge Delay setting is 345600 (4 days). The volume name is changed during delete so that a new volume with the same name can be immediately created. The management tool used to delete the volume should clean up any eDIR objects at delete time. The management tool also allows you to purge the deleted volume before the Purge Delay time elapses in order to free space on the volume.
To configure the Purge Delay time, enter the following at the server console:
nss /logicalVolumePurgeDelay=value
In this command, replace value with the actual number of seconds to delay the purge. For example, if you want to change the Purge Delay time from the default of 4 days to 1 day, set the value to 86400 by entering:
nss /logicalVolumePurgeDelay=86400
The Purge Delay change command is not permanent when entered from the command line. You must enter the command each time you restart the server. To make the new setting permanent, add the command to the autoexec.ncf file.
The volume salvage and file system salvage function separately. For information about configuring automatic purging for directories and files, see Section 19.2.2, Setting the Low and High Watermarks for Automatically Purging Deleted Files.
19.2.2 Setting the Low and High Watermarks for Automatically Purging Deleted Files
Automatic purging, or autopurging, begins when the volume’s low watermark is reached and continues until its high watermark is reached. The default low watermark is when free space is 10% or less of the total disk space. The default high watermark is when free space is at least 20% of the total disk space.
When free disk space falls below a low watermark, NSS begins autopurging the deleted files. When enough files are purged so that the free disk space increases to a percentage equal to or greater than the high watermark, the autopurge stops. Autopurging does not start again until free space again drops below the low watermark.
Figure 19-1 How Autopurging Works
The high and low watermarks can be configured at a pool level. The low watermark’s percentage can range from a minimum of 0% to a maximum of 98%. The high watermark’s percentage can range from a minimum 2% to a maximum of 100%. The high and low watermarks must be at least 2% apart from each other.
At the minimum setting of 0%, the low watermark activates the autopurge only when the system is totally out of free space. If it is set this low, the users are likely to get out-of-space errors when they try to save files to the full disk. Setting the low watermark to a percentage a little higher than 0% guarantees that autopurging begins before free space is completely used, and users are less likely to get out-of-space errors.
To configure the high and low watermarks, enter the following at the server console:
nss /PoolHighWaterMark=<poolname>:Percent
nss /PoolLowWaterMark=<poolname>:Percent
For example, to set the low watermark to 5% and the high watermark to 10% for pool p_users, enter
nss /PoolHighWaterMark=p_users:10
nss /PoolLowWaterMark=p_users:5