You can leverage the OES Storage Services (NSS) directory and user space quotas management to control how space is allocated in a Dynamic Storage Technology shadow volume pair. These space restriction systems work independently, with the lower value being the most restrictive if multiple types of space restrictions apply. NSS allocates the space as it is needed; the quota does not reserve the space. The NSS file system enforces the quotas set on a volume independently of other volumes on the system. For information about NSS quotas, see Managing Space Quotas for Volumes, Directories, and Users
in the Storage Services File System (NSS) Administration Guide for Linux.
Management of quotas for volumes in a DST pair can be a challenge because NSS and NCP management tools are designed to work on independent volumes. DST provides a unified quota management system that allows you to manage your disk space usage policy for DST shadow volume pairs. With the ncpcon quotas command, you can view the existing directory quotas and user quotas on the primary volume, and then easily set related quotas on the secondary volume based on those settings. The NSS file system independently enforces the quotas set on each volume.
The ncpcon quotas command provides the following capabilities:
You can view the amount of space that is allocated for an NSS directory or user on the primary volume, the secondary volume, and the combined space restriction.
You can synchronize the NSS directory or user quotas from the primary volume to the secondary volume. You can use the same settings, or you can specify a percentage to set smaller or larger quotas on the secondary volume.
To remove space restrictions for a user on the secondary volume, you can remove a user quota on the primary volume (which sets the user quota as unlimited), and then synchronize the unlimited quota value to the secondary volume.
To remove space restrictions on a directory on the secondary volume, you can set an unlimited directory quota on the primary volume, and then synchronize the unlimited quota value to the secondary volume.
In OES 11 SP1 and earlier, DST does not offer a unified quota system for the DST shadow volume pair. Table 12-1 and Table 12-2 summarize the impact of the ncpcon quotas command on quotas management for DST shadow volume pairs.
Table 12-1 Directory Quotas Management and Functionality for DST Shadow Volume Pairs
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Directory Quotas Management and Functionality for DST Volume Pairs in OES 11 SP1 and Earlier |
Impact of the ncpcon quotas Command in OES 2015 and Later |
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You must enable the Directory Quotas attribute for each NSS volume in the DST shadow volume pair. |
No change. |
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An administrator can use NCP tools to add, modify, or delete directory quotas on the primary volume. In NSS, each directory’s quota information is stored as metadata with the directory in the file system. If there is no directory quota, no information is stored. Only directories with active quota settings have quota information. If you disable space restrictions for a directory, NSS automatically removes the quota setting from the directory. If you set a directory quota to a very large value (or unlimited), you effectively remove space restrictions from the directory, and the directory still has an active quota setting. |
No change. The ncpcon quotas sync command does not synchronize deletions of directory quotas from the primary volume to the secondary volume. When you delete a directory quota, NSS removes the quota setting from the directory in the file system. In order to remove space restrictions on the directory instance on the secondary volume, you can set an unlimited quota for the directory instance on the primary volume, and synchronize the unlimited setting to the secondary volume. |
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NCP tools cannot be used to manage directory quotas on the secondary volume, because the secondary volume’s NCP/NSS binding is disabled while it is in the DST relationship. The secondary volume is mounted in NSS but not in NCP. |
As the root user, an administrator can synchronize the directory quotas settings to the secondary volume with the same or proportionally larger or smaller space allocation. Quotas synchronization can also be configured to run in a cron job. |
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An administrator can view directory quotas set on the primary volume. Secondary quotas settings are not available. |
As the root user, an administrator can view directory quotas set on the primary volume, the secondary volume, and the combined space restriction for each directory. |
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A user who is a directory trustee can view the directory quota set on the primary volume by using an NCP client. Directory quotas settings for the secondary volume are not available. |
No change. |
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The NSS file system independently enforces the directory quotas set on each volume. |
No change. |
Table 12-2 User Quotas Management and Functionality for DST Shadow Volume Pairs
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User Quotas Management and Functionality for DST Volume Pairs in OES 11 SP1 and Earlier |
Impact of the ncpcon quotas Command in OES 2015 and Later |
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You must enable the User Space Restrictions attribute for each NSS volume in the DST shadow volume pair. |
No change. |
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An administrator can use NSS tools to add, modify, or delete the user quotas on the primary volume. In NSS, user quota information is stored in the volume’s /_admin/Manage_NSS/Volume/<vol name>UserInfo.xml file. |
No change. The ncpcon quotas sync command can synchronize deletions of user quotas from the primary volume to the secondary volume. When a user quota is deleted, NSS does not delete the quota entry for the user. Instead, NSS changes the user quota setting in the volume’s /_admin/Manage_NSS/Volume/<vol name>UserInfo.xml file from some restriction to unlimited. The command synchronizes the unlimited setting to the secondary volume, which effectively removes the space restrictions for the user. The novcifs --user-quota-sync command duplicates all of the user quotas that are set on the primary volume to the secondary volume. |
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An administrator can use NSS tools to add, modify, or delete user quotas on the secondary volume. This has no relationship to the settings made on the primary volume. |
As the root user, an administrator can synchronize the user quotas settings from the primary volume to the secondary volume with the same or proportionally larger or smaller space allocation. Quotas synchronization can also be configured to run in a cron job. The interval to run the cron job depends on the nature of a company's setup and how often you add or change quotas in your environment. If quotas are regularly added throughout the day and require a quick synchronization, you might run the synchronization every hour. Otherwise, you might run it only once a day at a time when users are typically not active. If the quotas are managed only on certain days of the week or month, you can accordingly adjust how often and when the cron synchronization occurs. The load and time needed for quota synchronization depends on the number of directory quotas and user quotas to be synchronized. The more quotas there are to synchronize, the greater are the load and time required for the process. The load can be fairly intensive, but it is fairly brief. You can use a cron job to synchronize quotas at a time when users are typically not active. |
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Administrators can view the user quotas separately on the primary volume and the secondary volume, but not both in the same browser window. There is no report of the combined space restriction for each user. |
As the root user, an administrator can view user quotas set on the primary volume, the secondary volume, and the combined space restriction for each user. |
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The NSS file system independently enforces the user quotas set on each volume. |
No change. |