All,
When I reformatted to HTML, I forgot ro fix the code also - here is the
correct code:
#include <stdio.h>
#include <math.h>
#define NUM_BAYS 24
#define DRIVE_SIZE_GB 300
#define MTBF_YEARS 4
#define MTTR_HOURS_NO_SPARE 16
#define MTTR_HOURS_SPARE 4
int main() {
printf("\n");
printf("%u bays w/ %u GB drives having MTBF=%u years\n", NUM_BAYS,
DRIVE_SIZE_GB, MTBF_YEARS);
for (int num_drives=2; num_drives<=8; num_drives*=2) {
for (int num_parity=1; num_parity<=2; num_parity++) {
double mttdl;
int mtbf_hours = MTBF_YEARS * 365 * 24;
int total_num_drives = num_drives + num_parity;
int num_instances = NUM_BAYS / total_num_drives;
int num_spares = NUM_BAYS % total_num_drives;
double mttr = num_spares==0 ?
MTTR_HOURS_NO_SPARE : MTTR_HOURS_SPARE;
int total_capacity = num_drives * num_instances *
DRIVE_SIZE_GB;
if (num_parity==1) {
mttdl = pow(mtbf_hours, 2.0) / (total_num_drives *
(total_num_drives-1) * mttr );
} else if (num_parity==2) {
mttdl = pow(mtbf_hours, 3.0) / (total_num_drives *
(total_num_drives-1) * (total_num_drives-2) * pow(mttr, 2.0) );
}
printf(" - can have %u (%u+%u) w/ %u spares providing %u GB
with MTTDL of %.2f years\n",
num_instances,
num_drives, num_parity,
num_spares,
total_capacity,
mttdl/24/365/num_instances
);
}
}
}
Sorry about that
Kent
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