Product manual
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VTrak A-Class Product Manual Promise Technologies
Journal Size: The Journal is a type of circular log maintained on the disk used by the le system
to store what is going to change in the metadata before being written to the Meta Data LUN.
Journaling
is used on a le system for faster recovery in the event of a system crash or power failure. Recovery
is faster because a journal eliminates the need to check the entire le system when it is restarted.
The VTrak File System uses dedicated blocks on the Meta Data LUN for the Journal.
Journal Size
is one of the advanced conguration settings available to be set by the administrator. This cannot
be changed once the le system has been created. It is important for the overall performance of the le system
to have a journal that is neither too small nor too large. When a larger log size is chosen, recovery time will
be proportionately longer and the le system may consume more system resources (such as memory) during
normal operation affecting performance. On the other hand, if it is too small the journal data will be insufcient
to serve its primary function of helping to enable fast recovery. A Journal Size between 64MB (default value)
and 512MB should prove acceptable for performance. If the administrator prefers to use a value larger than
this recommended range, testing should be conducted to determine how performance is affected before the le
system is made available for use. The test should use representative system loads against varied journal sizes,
then pick whichever performs best.
Inode Ratio: The Inode or index node is a data structure in a les system that contains various matadata
about a le such as the size, socket, device node, location of the disk blocks where the contents is stored, and
other information except the contents and name of the le.
The Inode Ratio is the ratio of blocks on the Meta Data LUN that are reserved for exclusive use for inode data.
For example, a ratio of 1/7 (default value) means that one seventh of the blocks on the Meta Data LUN are
reserved for inode data. Increasing the ratio increases the number of inodes available in the le system meaning
that a larger number of les can be stored. If the available inode space on the Meta Data LUN are used up, no
more les can be stored on the le system regardless of how much space is available on the Data LUNs.
The default Inode ratio 1/7 should be more than enough, even for very large le systems.