[PDF] Parallels Server 5 Bare Metal

What are Disk Quotas?
Managing Resources
Disk quotas enable system administrators to control the size of Linux file systems by limiting the
amount of disk space and the number of inodes a Container can use. These quotas are known as
per-Container quotas or first-level quotas in Parallels Server Bare Metal. In addition, the Parallels
Server Bare Metal software enables the Container administrator to limit disk space and the number
of inodes that individual users and groups in that Container can use. These quotas are called peruser
and per-group quotas or second-level quotas.
By default, first-level quotas on your server are enabled (which is defined in the
/etc/vz/vz.conf configuration file), whereas second-level quotas must be turned on for each
Container separately (in the corresponding Container configuration files). It is impossible to turn on
second-level disk quotas for a Container if first-level disk quotas are off for that Container.
Parallels Server Bare Metal keeps quota usage statistics and limits in
/var/vzquota/quota. - a special quota file. The quota file has a special flag
indicating whether the file is “dirty”. The file becomes dirty when its contents become inconsistent
with the real Container usage. This means that when the disk space or inodes usage changes
during the Container operation, these statistics are not automatically synchronized with the quota
file, the file just gets the “dirty” flag. They are synchronized only when the Container is stopped or
when the server is shut down. After synchronization, the “dirty” flag is removed. If the server has
been incorrectly brought down (for example, the power switch was hit), the file remains “dirty”, and
the quota is re-initialized on the next Container startup. This operation may noticeably increase the
server startup time. Thus, it is highly recommended to shut down the server properly.
Disk Quota Parameters
The table below summarizes the disk quota parameters that you can control. The File column
indicates whether the parameter is defined in the global configuration file (G), in the Container
configuration files (V), or it is defined in the global configuration file but can be overridden in a
separate Container configuration file (GV).
Parameter Description File
DISK_QUOTA Indicates whether first-level quotas are on or off for all Containers or for an
individual Container.
DISKSPACE Total size of disk space the Container may consume, in 1-Kb blocks. V
DISKINODES Total number of disk inodes (files, directories, and symbolic links) the
Container can allocate.
QUOTATIME Grace period for the disk quota overusage, in seconds. The Container is
allowed to temporarily exceed its quota soft limits for no more than the
QUOTATIME period.
QUOTAUGIDLIMIT Maximum aggregate number of user IDs and group IDs for which disk
quota inside the given Container will be accounted. If set to 0, the UID and
GID quota are disabled.
GV
V
V
V
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