Availability In Real Terms
I blogged recently about a Dictionary of Non-Functional Requirements that we used as a basis for discussing NFR's; in another recent meeting we were going to discuss availability with the business, and I though it'd be worth defining 'availablility' in real terms - terms that any non-technical person could understand.
Here's the extra info, which is now included in the PDF version of the Dictionary I put up earlier.
|
1 full day
= 24 hours
= 1440 minutes
= 86400 seconds
|
Availability |
Required Up-time
(in minutes) |
Permitted Down-time
(in minutes / seconds) |
|
%99 |
1425.6 |
14.4 |
864 |
|
%99.9 |
1438.56 |
1.44 |
86.4 |
|
%99.99 |
1439.856 |
0.144 |
8.6 |
|
%99.999 |
1439.985 |
0.014 |
0.864 |
|
9am – 5pm
= 8 hours
= 480 minutes
= 28800 seconds
|
Availability |
Required Up-time
(in minutes) |
Permitted Down-time
(in minutes / seconds) |
|
%99 |
475.2 |
4.8 |
288 |
|
%99.9 |
479.55 |
0.48 |
28.8 |
|
%99.99 |
479.952 |
0.048 |
2.88 |
|
%99.999 |
479.995 |
0.004 |
0.288 |
|
1 month
= 30 days
= 720 hours
= 43200 minutes
= 2592000 seconds
|
Availability |
Required Up-time
(in hours) |
Permitted Down-time
(in hours / minutes) |
|
%99 |
712.8 |
7.2 |
432 |
|
%99.9 |
719.28 |
0.72 |
43.2 |
|
%99.99 |
719.928 |
0.072 |
4.32 |
|
%99.999 |
719.993 |
0.007 |
0.432 |
|
Maintenance Window |
% Availability (Daily / Weekly / Monthly) |
|
Daily |
Weekly |
Monthly |
|
5 minutes |
%99.652 |
%99.95 |
%99.988 |
|
15 minutes |
%98.958 |
%99.851 |
%99.965 |
|
60 minutes |
%95.833 |
%99.404 |
%99.861 |
Calculations based on a 24 hour day, 7 day week, 30 day month. |