APPENDIX D - HARD DISK UTILIZATION
CALCULATIONS
An important consideration in the configuration process is the
amount of hard disk space utilized. This appendix explains
how to calculate the amount of space a configuration will
occupy on the hard disk.
OIS Software and Tag Database
For calculations, the OIS software and tag database occupies
approximately 100 megabytes.
Displays
The total amount of hard disk space to allocate for storage of
displays varies. The minimum amount of space to allow should
be one megabyte. To calculate the amount of hard disk space
consumed by displays, use the formula:
No. of displays × average display size × retention factor
The amount of space needed for a single display varies from
four kilobytes for a simple menu to up to 40-kilobytes for a
complex display. The average display size depends on the complexity of the actual display files. Using a 40-kilobyte average
display size calculates a worst case amount. The utilization
example given later in this section uses a 15-kilobyte average
display file size.
When transferring a display source file and its associated symbol source files (DT) to the console, they initially reside on the
hard disk as PC (DOS) format files. They are then converted to
an OpenVMS format and reside in DT files in another directory. After being converted, the original DT files in PC format
still remain on the hard disk. After being converted, a display
(DT) source file must be processed using the graphical display
configuration tool. The result of this processing is a usable DU
display file and associated DL symbol files. The DU and DL
files occupy approximately the same amount of disk space as
their corresponding DT source files.
All three sets of display files must be considered when calculating the amount of hard disk space consumed by displays.
This determines the value used as the retention factor in the
calculation. After a display is processed and has no errors, its
associated DT files can be removed from the hard disk if
desired. The retention factor should be one if only the DU/DL
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files are retained on the hard disk, two if DU/DL and one set of
DT files, and three if DU/DL and both sets of DT files.
Trend Data
The minimum amount of space to allow is one megabyte. The
maximum depends on the size of the hard disk drive and how
much space is allocated for other functions.
Standard Trend
Use the following formula to calculate the disk space usage for
a standard trend (normal and fast):
(numsamples × 4 bytes) + 48 bytes
where:
numsamples
Total number of samples collected over a
certain period of time. The number of
samples is equal to:
time period ÷ collection resolution
Table D-1 gives examples of calculated trend data disk space
utilization for standard trends.
Table D-1. Standard Trend Data Disk
Space Utilization
Trend Type
Utilization per
Trend (bytes)
15 second, trended over 1 day
23,040 + 48
15 second, trended over 2 days
46,080 + 48
15 second, trended over 3 days
69,120 + 48
15 second, trended over 4 days
92,160 + 48
15 second, trended over 5 days
115,200 + 48
15 second, trended over 6 days
138,240 + 48
15 second, trended over 7 days
161,280 + 48
1 minute, trended over 1 day
5,760 + 48
1 minute, trended over 2 days
11,520 + 48
1 minute, trended over 3 days
17,280 + 48
1 minute, trended over 4 days
23,040 + 48
1 minute, trended over 5 days
28,800 + 48
1 minute, trended over 6 days
34,560 + 48
1 minute, trended over 7 days
40,320 + 48
Intermediate time frames can be calculated by interpolation.
For example, a 15-second trend, trended over eight hours:
8
------ × 23040 + 48 = 7728 bytes
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500 one-minute trends, trended over seven days:
( 500 × 40320 ) + 48 = 20.2 Mbytes
Enhanced Trend
The disk space usage for enhanced trends depends on the
variable being trended. Use one of the following formulas to
calculate the disk space usage for an enhanced trend:
ANALOG
(numevents × 12 bytes) + 48 bytes
DADIG
(numevents × 10 bytes) + 48 bytes
DANG
(numevents × 24 bytes) + 48 bytes
Digital type
(numevents × 10 bytes) + 48 bytes
RMSC
(numevents × 12 bytes) + 48 bytes
STATION
(numevents × 24 bytes) + 48 bytes
where:
numevents
Example:
Depends on the trend definition. The
maximum number of events the console
is to save on its hard disk is set during
definition of a trend. Refer to Defining a
Trend in Section 11 for further explanation.
100 ANALOG trends with 10,000 events saved per trend:
100 × ( 10000 × 12 + 48 ) = 12.0 M
Log Data
Custom Logs
Use the following formulas to calculate the disk space for custom log files:
1. Log definition files consume (approximately):
[6.5 kbytes + (6 bytes × no. of columns) × no. of rows] × no. of logs
defined
2. Log retention files consume (approximately):
(no. of rows × 132 characters) × total no. of retentions defined for all logs
3. Log output files consume (approximately):
(132 characters per row × no. of rows) × n
where:
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n
Number of log output files. Ranges from
one log output file to possibly 35 log output files per log (when logs are generated
faster than the printer can handle).
4. Log data files consume (approximately):
(8 bytes per dynamic value cell defined + 1.5 kbytes) × n
where:
n
SOE Logs
Number of log data files. Ranges from
one data file to possibly 35 data files per
log (when logs are generated faster than
the printer can handle).
Use the following formulas to calculate the disk space for SOE
log files:
1. Each data file consumes:
8 bytes × no. of events
Total = (8 × no. of events) × no. of SOE logs defined
2. Each output file consumes (approximately):
132 characters × no. of events
3. Each SOE retention consumes (approximately):
132 characters × no. of events
4. Each log is limited to nine retentions. Its data files may
range from one to 35 files per SOE log, similar for its output
files.
CONSIDERATIONS
The amount of hard disk space required by the console is
dynamic. The amount of space needed at any given time
depends on the operations or tasks the console is performing.
Use the formulas in this appendix to calculate the requirements, then add the following percentages to accommodate for
the dynamic needs of the console to insure optimum
performance:
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20 percent if configured for logging.
10 percent if not configured for logging.
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UTILIZATION EXAMPLE
The following characteristics are used in this example:
•
667 displays (15 kilobytes average display file size, DU/DL
and one set of DT files retained on the hard disk).
•
200 standard trends.
•
200 enhanced trends (100 ANALOG, 50 digital type, and
50 STATION).
•
500-megabyte formatted hard disk.
NOTE: The console can use a variety of different hard disk drives.
The example uses a 500-megabyte hard disk drive for calculations.
Table D-2 shows the calculations and remaining unused disk
space for this example utilization.
Table D-2. Example Utilization
Data
Utilization
Total
Bytes
OIS software and tag
database
100.0 M1
100.0 M
Displays
667 ¥ ( 15 k ¥ 2 ) = 20.0 M
120.0 M
200 at 15-sec resolution over 7
days = 32.3 M
152.3 M
Trends
2
Standard
200 ¥ ( 161280 + 48 ) = 32.3 M
Enhanced
200 with 10,000 events being saved
per trend = 29.0 M
181.3 M
100 ANALOG:
100 ¥ ( 10000 ¥ 12 + 48 ) = 12.0 M
50 digital type:
50 ¥ ( 10000 ¥ 10 + 48 ) = 5.0 M
50 STATION:
50 ¥ ( 10000 ¥ 24 + 48 ) = 12.0 M
Unused disk space3 = 318.7 M
NOTE:
1. Assumes a default database of 30,000 tags.
2. Depends on the types of trends being configured. Use the worst possible case for number of
trends.
3. Available for other functions such as archiving and logging. Based on a 500-megabyte hard disk
drive.
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