Installation guide

44
Wi-Fi Location-Based Services—Design and Deployment Considerations
OL-11612-01
Installation and Configuration
Note The df –H command is used here because it is a commonplace practice for most computer disk
manufacturers to assume 1 GB = 1,000,000,000 bytes. The –H option displays output as powers of 1000
rather than 1024. Use df –h if your preference is for the contrary.
The df display output shown here is for a location appliance containing a hard disk drive with an
unformatted capacity of 80 GB. Notice that there are two main file systems defined: /dev/sda1, which is
the Linux boot file system; and /dev/sda2, which contains the root directory as well as the location
application and all databases. You can clearly see from the display above that only 5 percent of all
available space on /dev/sda2 is currently being used. That being the case, there is an abundance of free
space available and probably no need to defragment at this time.
You can use the information in the df output along with the knowledge of the size of the location
database (from DB Disk Memory described in Memory Information, page 43) to approximate the
maximum recommended size to which the location server database should be allowed to grow. At first
glance, this may appear intuitive; that is, max recommended database size = total available disk space –
(OS size + location application size). However, you should also account for the creation of a flat file that
is used during the database backup process. Using the formula below, you can calculate the maximum
recommended size of the location database including this additional free space plus a small additional
amount to account for system overhead (such as the downloading of an location appliance upgrade
image):
Where:
• MaxDatabaseSize is the maximum recommended size of the database in bytes
Note MaxDatabaseSize assumes the user has performed a cleanup of any residual location server
upgrade images. Multiple residual upgrade images may consume additional free space
exceeding these allotments.
• TotalSpace is the total amount of available space on /dev/sda2 in GB.
• OSApplSpace is the amount of space occupied by the Linux OS and the location server application
on /dev/sda2. This can be calculated for the example shown above as:
((the amount of used disk space in Gigabytes) – (the current size of the location server database in
Gigabytes)).
The current size of the location server database can be found at WCS > Location Server > Advanced
Parameters > DB Disk Memory. In the case of the system used for this example, DB Disk Memory =
24,608,768 bytes or .024608768 GB. Thus, OSApplSpace = (3.2 - .024608768 GB) or 3.175391232 GB.
Substituting these values for TotalSpace and OSApplSpace into the equation, you can calculate the
maximum recommended size to which the location server should be allowed to grow as (77 GB –
3.175 GB) / 2.3 = 73.825 / 2.3 = 32.099 GB. Therefore, to ensure proper operation of the database
backup mechanism in a location appliance with an 80 GB unformatted capacity hard disk drive, the
maximum recommended size of the location database (as indicated by DB Disk Memory) should not be
allowed to exceed approximately 32 GB.
3.2
eOSApplSpacTotalSpace
eSizeMaxDatabas
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=