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RamSan-500 User’s Manual 33 of 48
There are four different configuration options, Tuning, Read Ahead, Sync
Always, and Dirty Threshold Percent. There are several options for each
of these parameters that affect the behavior of the Cache:
• Tune Cache For – This parameter controls the cache line size and
how the Cache works with the back end Flash Array. The two
options are:
o IOPS – Use a smaller cache line size and send smaller
accesses to the RAID controller. This setting is
recommended for storage workloads that tend to us 64KB
or smaller accesses (most database workloads).
o Bandwidth – Use a larger cache line size and send large
accesses to the RAID that access multiple Flash modules in
parallel. This setting is recommended for data acquisition
or for a small number of users that need high bandwidth
(some data warehouse workloads).
• Read Ahead – The read ahead setting controls whether the cache
attempts to read additional data ahead of the location of a read.
This can help improve performance in a highly sequential read
environment, but wastes cache space under a random workload.
The higher the setting the more read ahead is attempted.
• Sync Always – This parameter controls whether the cache will
always attempt to sync to the back end Flash. When the box is
checked, this feature is enabled.
• Dirty Threshold Percent – This parameter controls how much of the
cache can be used for storing dirty data (data that has been
written to Flash but has not yet been written to disk) before the
system gives syncing the dirty data to Flash a higher priority.
4.13 Viewing the Logs with the Web Monitor
Perhaps the most important part of the Web monitor is the system event
log. This log keeps track of all events that occurred within the system. If
you are having trouble with your system, be sure to open the system
event log and check this information.