Managing quotas on virtual volumes
Three types of quotas are maintained for each virtual volume:
- Explicit User/Group Quotas. A quota explicitly created to impose restrictions on an individual user or group, defining a unique set of thresholds.
- Default User/Group Quotas. A quota set automatically for all users and groups that do not have explicit quotas, set by defining a set of Quota Defaults (thresholds) for creating a quota automatically when a file is created or modified in the virtual volume. .
Default quotas for virtual volumes operate in the same way as those defined for file systems. User (Group) quota defaults define a set of thresholds for creating a quota for a user (or group) the first time that user (or group) saves a file in the virtual volume.
Initially, quota defaults are not set. When activity occurs in the virtual volume, it is tracked, but quotas are not automatically created. When at least one threshold is set to a non-zero value, a User or Group quota (as appropriate) will be created for the owner of the directory at the root of the virtual volume.
- Virtual Volume & Quotas. A virtual volume quota tracks the space used within a specific directory on the virtual volume . A quota can be explicitly created to define a set of thresholds restricting all operations in the virtual volume, unrelated to which user or group initiated them.
When Usage and File Count limits are combined, the server will enforce the first quota to be reached.
The server treats the virtual volume 'root' directory, together with all its sub-directories, as a self-contained file system. The virtual volume tracks its usage of space and number of files, to provide a way of monitoring file system usage. This tracking allows quotas to be imposed on disk space usage, as well as the total number of files.
Quotas can be set for the entire virtual volume, and on individual users, and on groups of users. Default user and group quotas can be defined, and in the absence of explicit user or group quotas, the default quotas apply.
The following caveats apply in measuring the virtual volume status against quota thresholds:
- Metadata and snapshot files. Neither file system metadata nor snapshot files count towards the quota limits.
- Symbolic link calculation. Files with multiple hard links pointing to them are included only once in the quota calculation. A symbolic link adds the size of the symbolic link file to a virtual volume and not the size of the file to which it links.
Advertising NFS exports for Virtual Volumes
This feature enables or disables the reporting of 'fake' NFS exports at the roots of virtual volumes.
A file system can contain NFS exports at the root of the file system, for example, /home, and also virtual volumes for users' home directories, for example, /fred and /joe. When the automounter on an NFS client mounts one of these home directories, it sends a request to the server to obtain the list of exports. This is the same request that's used by the showmount -e command. On receiving this list, it selects the most suitable export to mount.
If, for example, the automounter has been told to mount /home/fred but the only suitable export it finds is /home, it first mounts /home, then changes directory to /fred. Although this is fine for general file system operation, and indeed many mounts are created this way, it does mean that quota information may not be returned correctly. The reason for this is that because the client has mounted the export /home, the free space that's reported for the mount is that of the entire file system, not of the virtual volume /fred.
In order to enable the server to report the correct quota information for the mount, the client must mount /home/fred directly, rather than mounting /home and then changing directory to /fred. An obvious way to achieve this is to add an export /home/fred. However, having to manually add an export at the root of every virtual volume is time consuming.
Therefore, the server has the facility to report a 'fake' NFS export at the root of each virtual volume. In the scenario above, with a single export /home at the root of the file system, the server reports the exports /home, /home/fred and /home/joe. On receiving this list, the client now sees that the most suitable export is /home/fred, so it mounts that path directly, therefore ensuring that the correct quota information is returned to the user fred.
Take the following information into account when using this feature:
- If UDP is used to transport MOUNT requests, only the first 64KiB of NFS export information is returned. So, TCP is recommended to ensure the complete list of NFS exports is always returned.
- The server returns a maximum of 1000 mounts in response to the showmount -d command.
- The Linux autofs4 client mounts all available exports, using a separate socket for each. So, if this feature causes a large number of exports to be advertised, Linux clients can end up with a large number of mounts. This can cause port exhaustion and can cause Linux clients to run very slowly.
For further information, see the nfs-export-advertise-for-virtual-volumes CLI command man page. This command also refreshes the list of exports manually and configures the interval at which automatic refreshes of the list occur. The list is always refreshed immediately when an export or virtual volume is added or removed, but it is also refreshed in the background at regular intervals to ensure other changes, such as directory renames, are reflected in the export list.
Viewing and modifying virtual volume quotas
This page lists all the current quotas for the specified virtual volume or the specified file systems, and allows a quota's details to be viewed.
Navigate to .
Fill in the check box next to the virtual volume to view or modify and then click View Quotas to display the Quotas page.
The following table describes the fields on this page:
Field/Item Description Virtual Volume Identifies the virtual volume to which these quotas apply:
- EVS/File System: EVS and file system on which the virtual volume resides.
- Virtual Volume Name: Name of the virtual volume.
- Path: Directory on which the virtual volume has been created.
Filter Because many user/group quotas can exist on a virtual volume, the server provides a way to filter the list.
- Filter Quota Type: You can filter on All Types (default), Users, Groups or Virtual Volumes.
- Where User/Group Account matches: The user or group name to be matched. The wildcard character * is permitted.
User/Group Account (also known as the target) A quota name can consist of:
- A CIFS domain and user or group name, such as bb\Smith or bb\my_group (where bb is a domain, Smith is a user and my_group is a group).
- An NFS user or group such as richardb or finance (in which richardb is an NFS user and finance is an NFS group).
A name can be empty (if the quota is a virtual volume quota) or 0 (if the quota was created for the owner of the directory at the root of the virtual volume).
Quota Type Type of source of virtual volume activity. Possible values are User, Group, or Virtual Volume . The type applies to anyone initiating activity in the entire virtual volume, and only one quota with this target type may exist on each virtual volume. Created By Method of quota creation. Possible values are Automatically Created (created using a quota default) or User Defined (where the quota was set uniquely for one particular quota). Usage Limit Overall limit set for the total size of all files in the virtual volume owned by the target of the quota. File Count Limit Overall limit set for the total number of files in the virtual volume owned by the target of the quota. details Opens the Details page, in which you can view and edit the configuration of the selected quota. add Opens the Add Quota page. delete Deletes a selected quota. refresh cache Clears the NAS Manager cache and repopulates the cache with the relevant objects. (This is different than clicking the browser refresh button, which picks up any recent updates without clearing the cache.) User Defaults Opens the User Quota Defaults page, in which you can set or change the defaults for users.
Group Defaults Opens the User Quota Defaults page, in which you can set or change the defaults for groups. Download Quotas Downloads a comma-separated value (CSV) file containing all available quota information for the virtual volume.
Setting user/group defaults
Procedure
Navigate to to display the Quotas page.
Click User Defaults to display the User Quota Defaults page.
The following table describes the fields on this page:
Field/Item Description EVS/File System The EVS and file system on which the user quota applies. Virtual Volume Name Name of the virtual volume to which a user quota created using these defaults is assigned. This option only appears when setting the quotas for a virtual volume. Automatically create quotas for domain users This option only appears for group quotas. It creates quotas for individual domain users. Usage Limit Amount of space to enable in Bytes: KiB, MiB, GiB, TiB, PiB, or EiB. Hard Limit When enabled, the amount of space specified in the Limit field cannot be exceeded. Warning Percentage of the amount of space specified in the Limit field at which a Warning alert will be sent. Severe Percentage of the amount of space specified in the Limit field at which a Severe alert will be sent. File Count Limit Maximum number of files to allow in this virtual volume. Hard Limit When enabled, the number of files specified in the Limit field cannot be exceeded. Warning Percentage of the number of files specified in the Limit field at which a Warning alert will be sent. Severe Percentage of the number of files specified in the Limit field at which a Severe alert will be sent. Log Quota Events in the managed server's Event log Selecting this check box sets the default for all users or groups to have quota events logged in the server's event log. clear defaults Prevents additional user quota defaults from being created in the virtual volume.
Exporting quotas for a specific virtual volume
You can export quotas for a specific virtual volume using the NAS Manager.
Navigate to to display the Virtual Volumes & Quotas page.
Select a virtual volume and click View Quotas to display the Quotas page.
Click Download Quotas for this Virtual Volume.
Save the quota information to as a comma-separated value (CSV) file.
You also can choose to display the quota information in an application.