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Command cluster statistics www.gateway.com
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Statistic Description
Write Cluster Rate This is the percentage of the number of write commands
that are part of a cluster versus the total number of write
commands that have been issued. This gives an indication
of the sequential nature of the data access pattern from
the host and of the performance of the writeback cache.
RAID 5/50 Full Stripe Write Rate This is the percentage of the amount of data that is
written as a full stripe write versus the total amount of
data written. This gives an indication of the sequential
nature of the data access pattern from the host and of the
performance of the writeback cache for RAID 5/50 drive
ranks.
Command Cluster Count When the controller clusters write commands, it may
cluster a large number of them together. These statistics
record the average and maximum number of commands
the controller clusters and the percentage for each one of
these values.
Command Cluster Interval In determining whether to cluster write commands or not,
the controller searches back in the command queue
whenever it receives a new write command. In a
multi-threaded operating system, commands from each
thread may be interspersed with commands from another
thread. The controller must check more than the
immediately previous command. The controller searches
back for a number of commands to try to determine if the
new command is exactly sequential to any one of these
previous commands. If it is, the controller determines that
it can cluster these commands.
These statistics record the average and maximum number
of commands the controller must search back for when it
finds a sequential command match and the percentage
for each one of these values.